Method of separating a polymer from a solvent

ABSTRACT

A method of separating a polymer-solvent mixture is described wherein a polymer-solvent mixture is heated prior to its introduction into an extruder comprising an upstream vent and/or a side feeder vent to allow flash evaporation of the solvent, and downstream vents for removal of remaining solvent. The one-step method is highly efficient having very high throughput rates while at the same time providing a polymer product containing low levels of residual solvent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 10/648,524, filed Aug. 26, 2003, now U.S. Pat. No. 6,949,622which is incorporated herein in its entirety.

BACKGROUND OF THE INVENTION

The preparation of polymeric materials is frequently carried out in asolvent from which the polymer product must be separated prior tomolding, storage, or other such applications. This is the case in themanufacture of polyetherimide prepared by condensation polymerization ofa dianhydride with a diamine in ortho-dichlorobenzene solution. Manyother polymers are similarly prepared in solution and require a solventremoval step in order to isolate the polymer product. Illustrativepolymers include interfacially-prepared polycarbonates, polysulfones,interfacially-prepared polycarbonate esters, and the like. The solventfrequently plays an indispensable role in polymer manufacture, providingfor thorough mixing of reactants and for reducing the viscosity of thereaction mixture to provide for uniform heat transfer during thepolymerization reaction itself. The solvent may further facilitateproduct purification by enabling the polymer product to be treated withwater, aqueous acids and bases, and drying agents prior to solventremoval. Additionally, because a polymer solution is typically much lessviscous than a molten polymer, the polymer solution is generally moreeasily filtered than the molten polymer.

Due to the pervasive use of solvent solutions in the manufacture orprocessing of polymeric material, there remains a need in the art toprovide a convenient and cost-effective method and system to isolate apolymer from a polymer-solvent mixture.

The formation of blends or filled polymeric material may be effected bycompounding a melt of the polymer with the additional polymer or filler.To prepare a polymer product having uniformly dispersed filler or touniformly disperse an additional polymer, high shear rates, extendedcompounding and extruding times, and high heat may be required. The longresidence times of compounding and high heat render the polymer productsusceptible to discoloration and degradation of desired physicalproperties.

There also remains a need for an efficient and simple method to preparea polymer product comprising uniformly dispersed filler.

BRIEF SUMMARY OF THE INVENTION

Disclosed herein is a method for separating a polymer from a solventcomprising introducing a superheated polymer-solvent mixture to anextruder, wherein the extruder comprises an upstream vent and adownstream vent; removing solvent from the superheated polymer-solventmixture via the upstream vent and the downstream vent; and isolating apolymer product from the superheated polymer-solvent mixture; andwherein the polymer-solvent mixture comprises a polymer and a solvent,wherein the amount of polymer in the polymer-solvent mixture is lessthan or equal to about 75 weight percent based on the total weight ofpolymer and solvent.

In another embodiment, a system for separating a polymer from a solventcomprises a means for superheating a polymer-solvent mixture; and anextruder in communication with the means for superheating a polymersolvent mixture, wherein the extruder comprises an upstream vent and adownstream vent.

In yet another embodiment, a method of preparing a filled polymercomprises introducing a superheated polymer-solvent mixture to anextruder, wherein the extruder comprises an upstream vent and adownstream vent, and wherein the superheated polymer-solvent mixturecomprises a filler; removing solvent from the superheatedpolymer-solvent mixture via the upstream vent and the downstream vent;and isolating a filled polymer from the polymer-solvent mixture, whereinthe polymer comprises a filler.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates one embodiment of a system for separating apolymer-solvent mixture, the system comprising a side feeder with a ventand a twin-screw extruder having one upstream vents and four downstreamvents;

FIG. 2 illustrates another embodiment comprising two side feeders eachequipped with a kneading block and vent;

FIGS. 3 and 4 are SEM micrographs of polyetherimide-polyphenylene etherblend isolated from a solution; and

FIG. 5 illustrates a rheology graph for a polyetherimide-fumed silicablend and polyetherimide control.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed herein are methods of separating polymer-solvent mixtures intotheir polymer and solvent components. Also disclosed are systems foreffecting the separation of polymer-solvent mixtures. Finally, a methodof preparing a polymer product comprising uniformly dispersed filler isdisclosed.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise.

“Optional” or “optionally” means that the subsequently described eventor circumstance may or may not occur, and that the description includesinstances where the event occurs and instances where it does not.

As used herein, the term “substantially all” means 95 percent or more.

As used herein, a polymer “substantially free of solvent” contains lessthan about 1000 parts per million solvent.

As used herein, the term “solvent” can refer to a single solvent or amixture of solvents.

In one aspect, a method relates to separating a polymer from a solvent.Typically polymer-solvent mixtures are solutions, which comprise one ormore polymers dissolved in one or more solvents. Alternatively, apolymer-solvent mixture may be one or more solvents dissolved in one ormore polymers, for example, in a polyetherimide containingortho-dichlorobenzene (ODCB), or polyetherimide-polyphenylene ethercontaining ODCB. Also contemplated as polymer-solvent mixtures arepolymer and solvent and further including a filler and/or an additive.

As noted, a method for separating polymer-solvent mixtures and anapparatus, herein referred to as a system, for accomplishing the same isdisclosed. In an exemplary embodiment, the polymer-solvent mixture maybe fed into a vented extruder configured to have sufficient volume topermit efficient flash evaporation of solvent from the polymer-solventmixture, for even very dilute solutions. Preferably the polymer-solventmixture is heated prior to being feed into the extruder. Heating vesselsare suitable for holding the polymer-solvent mixture prior to itsintroduction into the extruder. The heated polymer-solvent mixture mayfurther be heated by means of a heat exchanger or exchangers. Pumps suchas gear pumps may be used to transfer the polymer-solvent mixturethrough one or more heat exchangers.

The feed inlet through which the polymer-solvent mixture is fed to thefeed zone of the extruder may be in close proximity to a nearby vent.The extruder vent upstream of the feed inlet, which is used to effectthe bulk of the solvent removal, is herein described as an upstreamvent. The upstream vent may be operated at atmospheric or subatmosphericpressure. The extruder, the feed inlet, and the upstream vent areconfigured to provide the volume needed to permit efficient flashevaporation of solvent from the polymer-solvent mixture. A vent locateddownstream of the feed port of the extruder is typically run atatmospheric pressure, but preferably at subatmospheric pressure and isdescribed herein as a downstream vent.

The extruder may further comprise a side feeder equipped with a sidefeeder vent which provides for added volume and serves to trap andreturn polymer particles entrained by the escaping solvent vapors. Theupstream vent nearby the feed inlet and the side feeder vent may beoperated at atmospheric or subatmospheric pressure. A downstream ventcompletes the solvent removal process to provide a polymer productsubstantially free of solvent.

According to one embodiment, the polymer-solvent mixture is first heatedunder pressure to produce a superheated polymer-solvent mixture, whereinthe temperature of the superheated mixture is greater than the boilingpoint of the solvent at atmospheric pressure. Typically, the temperatureof the superheated polymer-solvent mixture will be about 2° C. to about200° C. higher than the boiling point of the solvent at atmosphericpressure. Within this range, a temperature of less than or equal toabout 150° C. can be employed, with less than or equal to about 100° C.preferred. Also preferred within this range is a temperature of greaterthan or equal to about 10° C., with greater than or equal to about 50°C. more preferred. In instances where there are multiple solventspresent, the polymer-solvent mixture is superheated with respect to atleast one of the solvent components. Where the polymer-solvent mixturecontains significant amounts of both high and low boiling solvents, itis sometimes advantageous to superheat the polymer-solvent mixture withrespect to all solvents present (i.e., above the boiling point atatmospheric pressure of the highest boiling solvent). Superheating ofthe polymer-solvent mixture may be achieved by heating the mixture underpressure.

Superheating may be described as the temperature a condensable gas isabove its boiling point at its current pressure. The degree ofsuperheat, (P₁ ^(v)-P_(t)), to characterize superheating, may be definedas the difference between the equilibrium pressure of the solvent in thevapor phase (P₁ ^(v)) and the total pressure in the space of theextruder where the devolatilization process takes place (P_(t)) as apositive value. In another embodiment, the flash separation of thesolvent from the polymer-solvent mixture may be accomplished by applyingvacuum to the heated mixture so the surrounding pressure is lower thanthe vapor pressure of the solvent in the mixture. This method is alsodescribed herein as superheating as the degree of superheat (P₁^(v)-P_(t)) is a positive value. A polymer-solvent mixture that is keptat a temperature below the boiling point of the solvent at atmosphericpressure can be in a superheated state as long as the surroundingpressure is lower than the vapor pressure of the solvent at thetemperature of the mixture.

When the polymer-solvent mixture is pressurized, the system may comprisea pressure control valve downstream of the heat exchanger, if used, ordownstream of the feed tank. The pressure control valve preferably has acracking pressure higher than atmospheric pressure. The crackingpressure of the pressure control valve may be set electronically ormanually and is typically maintained at from about 1 pounds per squareinch (psi) (0.07 kgf/cm²) to about 350 psi (25 kgf/cm²) aboveatmospheric pressure. Within this range, a cracking pressure of lessthan or equal to about 100 psi (7.0 kgf/cm²) can be employed, with lessthan or equal to about 50 psi (3.5 kgf/cm²) above atmospheric pressurepreferred. Also preferred within this range is a cracking pressure ofgreater than or equal to about 5 psi (0.35 kgf/cm²), with greater thanor equal to about 10 psi (0.7 kgf/cm²) above atmospheric pressure morepreferred. The back pressure generated by the pressure control valve istypically controlled by increasing or decreasing the cross sectionalarea of the valve opening. Typically, the degree to which the valve isopen is expressed as percent (%) open, meaning the cross sectional areaof valve opening actually being used relative to the cross sectionalarea of the valve when fully opened. The pressure control valve preventsevaporation of the solvent as it is heated above its boiling point.Typically, the pressure control valve is attached (plumbed) directly toan extruder and serves as the feed inlet of the extruder. A suitablepressure control valve includes a RESEARCH® Control Valve, manufacturedby BadgerMeter, Inc.

As mentioned previously, the extruder may comprise a side feedercomprising a vent to aid in the removal of solvent from thepolymer-solvent mixture. The extruder in combination with the sidefeeder is equipped with one or more vents in close proximity to theextruder feed inlet, such as a pressure control valve. The side feederis typically positioned in close proximity to the feed inlet throughwhich the polymer-solvent mixture is introduced into the extruder,preferably upstream from the feed inlet. For example, FIG. 2 illustratesan extruder (36) comprising two side feeders (37) and (38). Feed inlet(39) is shown in close proximity to the side feeders (37) and (38). Ithas been found advantageous that the side feeder comprises a feeder ventoperated at about atmospheric pressure or subatmospheric pressure.Alternatively, a side feeder feed inlet may be attached to the sidefeeder itself in which instance the side feeder feed inlet is attachedto the side feeder at a position between the point of attachment of theside feeder to the extruder and the side feeder vent. In yet anotheralternative, the polymer-solvent mixture may be introduced through feedinlets which may be attached to the side feeder, the extruder, or toboth extruder and side feeder.

Typically, the side feeder used according to the method is short, havinga length to diameter ratio (L/D) of about 20 or less, preferably about12 or less. The side feeder is typically not heated and functions toprovide additional cross sectional area within the feed zone of theextruder thereby allowing higher throughput of the solvent-polymermixture. The side feeder may be of the single-screw or the twin-screwtype. Typically, the twin-screw type side feeder is preferred. The screwelements of the side feeder are configured to convey polymer (which isdeposited in the side feeder as the solvent rapidly evaporates) back tothe main channel of the extruder. Typically, the side feeder is equippedwith at least one vent located near the end of the side feeder mostdistant from the point of attachment of the side feeder to the extruder.In instances in which a pressure control valve is attached to the sidefeeder it is preferably attached between the side feeder vent and thepoint of attachment of the side feeder to the extruder.

As mentioned, the side feeder screw elements are conveying elementswhich serve to transport deposited polymer into the extruder. In oneembodiment the side feeder screw elements comprise kneading elements inaddition to conveying elements. Side feeders comprising kneading screwelements are especially useful in instances in which the evaporatingsolvent has a tendency to entrain polymer particles in a directionopposite that provided by the conveying action of the side feeder screwelements and out through the vent of the side feeder. The extruder canbe similarly equipped with kneading screw elements between the point ofintroduction of the polymer-solvent mixture and one or more of theupstream vents. As in the side feeder, the kneading extruder screwelements act as mechanical filters to intercept polymer particles beingentrained by the solvent vapor moving toward the vents.

The extruder used in the method and system may comprise any number ofbarrels, type of screw elements, etc. as long as it is configured toprovide sufficient volume for flash evaporation of the solvent as wellas the downstream devolatilization of remaining solvent. Exemplaryextruders include a twin-screw counter-rotating extruder, a twin-screwco-rotating extruder, a single-screw extruder, or a single-screwreciprocating extruder. A preferred extruder is the co-rotating,intermeshing (i.e. self wiping) twin-screw extruder.

In one embodiment, the extruder preferably has a set barrel temperaturegreater than 190° C., preferably greater than or equal to about 200° C.In one embodiment the extruder comprises heated zones. In oneembodiment, the heated zones of the extruder are operated at one or moretemperatures of 190° C. to about 400° C. The expression wherein theextruder is operated at a temperature of 190° C. to about 400° C. refersto the heated zones of the extruder, it being understood that theextruder may comprise both heated and unheated zones. Within thisembodiment, the temperature of the heated zones may be greater than orequal to about 200° C., preferably greater than or equal to about 250°C., and even more preferably greater than or equal to about 300° C.

In general, as the feed rate of the polymer-solvent mixture is increaseda corresponding increase in the screw speed must be made in order toaccommodate the additional material being fed to the extruder. Moreover,the screw speed determines the residence time of whatever material isbeing fed to the extruder, here a polymer-solvent mixture. Thus, thescrew speed and feed rate are typically interdependent. It is useful tocharacterize this relationship between feed rate and screw speed as aratio. Typically the extruder is operated such that the ratio ofstarting material introduced into the extruder in kilograms per hour(kg/hr) to the screw speed expressed in revolutions per minute (rpm)falls about 0.0045 to about 45, preferably about 0.01 to about 0.45. Forexample, the ratio of feed rate to screw speed where the polymer-solventmixture is being introduced into the extruder at 400 kilograms per hourinto an extruder being operated at 400 rpm is 1. The maximum and minimumfeed rates and extruder screw speeds are determined by, among otherfactors, the size of the extruder, the general rule being the larger theextruder the higher the maximum and minimum feed rates. In oneembodiment the extruder operation is characterized by a ratio of a feedrate in kilograms per hour to an extruder screw speed in revolutions perminute, the ratio being between about 0.0045 and about 45. In analternate embodiment the extruder operation is characterized by a ratioof a feed rate in pounds per hour to an extruder screw speed inrevolutions per minute, the ratio being between about 0.01 and about0.45.

The system may optionally further comprise one or more condensingsystems to collect the solvent removed by the upstream vent, downstreamvent and/or side feeder vent. The vents may be connected to a solventremoval and recovery manifold comprising solvent vapor removal lines, acondenser and a liquid solvent receiving vessel. Any solvent collectionsystem known in the art may be used to effect the solvent recovery viathe vents.

In one embodiment the superheated polymer-solvent mixture passes throughthe pressure control valve into the feed zone of the extruder, which dueto the presence of the aforementioned vents (upstream extruder ventand/or side feeder vent) may be at atmospheric pressure. The solventpresent in the superheated polymer-solvent mixture undergoes sudden andrapid evaporation thereby effecting at least partial separation of thepolymer and solvent, the solvent vapors emerging through the upstreamvents. Additionally, the extruder is equipped with at least onedownstream vent operated at subatmospheric pressure, which serves toremove solvent not removed through the upstream vent and/or side feedervent. One downstream vent may be used, but preferably at least twodownstream vents are used. Generally, from about 50 to about 99 percent,preferably from about 90 to about 99 percent of the solvent present inthe initial polymer-solvent mixture is removed through the upstream ventand/or side feeder vent and a substantial portion of any solventremaining is removed through the downstream vent operated atsubatmospheric pressure.

The vent operated at about atmospheric pressure, whether it is anupstream vent or a side feeder vent, is operated at the pressure of thesurroundings (in the absence of an applied vacuum), typically about 750millimeters of mercury (mm of Hg) or greater.

The vent operated at subatmospheric pressure, whether it is an upstreamvent, side feeder vent, or downstream vent, may be maintained at lessthan or equal to about 750 millimeters of mercury (mm of Hg), preferablyabout 25 to about 750 mm Hg as measured by a vacuum gauge. Within thisrange, the vent may be operated at greater than or equal to about 100mm, preferably greater than or equal to about 250 mm and even morepreferably greater than or equal to about 350 mm of mercury. Also withinthis range the vents may be operated at less than or equal to about 600mm, preferably less than or equal to about 500 mm, and more preferablyless than or equal to about 400 mm of mercury of vacuum.

In one embodiment, the upstream vent and side feeder vent surroundingthe feed inlet of the extruder may be operated at subatmosphericpressure. In this embodiment, the pressure at the upstream vent and sidefeeder vent are selected and monitored during processing to preventexcessive foaming of the mixture that may result in clogging of thevents, side feeder and/or the condensing system downstream of theextruder.

In one embodiment the polymer-solvent mixture is introduced into anevaporator or distillation apparatus to concentrate the polymer-solventmixture prior to its introduction to the extruder. The evaporator ordistillation apparatus is preferably upstream from the extruder and indirect communication with the extruder via a pressure control valveattached directly to the extruder.

In one embodiment the superheated polymer-solvent mixture is introducedthrough multiple pressure control valves located on the extruder and theside feeder. A system comprising two side feeders and two pressurecontrol valves, the first of the pressure control valves communicatingdirectly with the feed zone of the extruder (i.e. attached directly tothe extruder), and the second of the pressure control valves beingattached to one of the side feeders, the second of the pressure controlvalves being said to communicate with the extruder via the side feeder.Alternatively, it is possible to have a system in which there is nopressure control valve in direct communication with the extruder, havinginstead multiple side feeders each of which is equipped with at leastone pressure control valve.

In another preferred embodiment the polymer-solvent mixture is filteredprior to its introduction into the extruder. The polymer-solvent mixturemay be filtered prior to and/or after heating or superheating.

The polymer-solvent mixture that is introduced into the extrudercomprises a solvent and a polymer, wherein the amount of polymer is lessthan or equal to about 99 weight percent based on the total of polymerand solvent. Within this range the amount of polymer may be less than orequal to about 75 weight percent, with less than or equal to about 60more preferred, and less than or equal to about 50 weight percent basedon the total of polymer and solvent more preferred. Also within thisrange, the weight percent of polymer may be greater than or equal toabout 5, with greater than or equal to about 20 preferred, and greaterthan or equal to about 40 weight percent based on the total of polymerand solvent more preferred.

Polymer-solvent mixtures comprising less than about 30 percent by weightsolvent are at times too viscous to be pumped through a heat exchanger,one of the preferred methods for superheating the polymer-solventmixtures. In such instances it is possible to superheat thepolymer-solvent mixture by other means, for example, heating thepolymer-solvent mixture in a extruder, or a helicone mixer, or the like.The polymer-solvent mixture may be superheated by means of a firstextruder. The superheated polymer-solvent mixture emerging from thefirst extruder may be transferred through a pressure control valve intoa second devolatilizing extruder equipped according to the method withat least one vent operated at subatmospheric pressure, optionally one ormore vents operated at about atmospheric pressure, and at least one sidefeeder equipped with at least one vent being operated at atmosphericpressure. In one embodiment, the die face of the first extruder mayserve as the pressure control valve, which regulates the flow ofsuperheated polymer-solvent mixture into the second devolatilizingextruder. In this embodiment the superheated polymer-solvent mixture isintroduced directly from the die face of the first extruder into thefeed zone of the second devolatilizing extruder. The first extruder maybe any single-screw extruder or twin-screw extruder capable ofsuperheating the polymer-solvent mixture.

The polymer product emerges from the extruder as an extrudate, which maybe pelletized and dried before further use. In some instances thepolymer product, notwithstanding the action of the upstream, downstream,and/or side feeder vents present, may contain an amount of residualsolvent which is in excess of a maximum allowable amount which rendersthe polymer unsuitable for immediate use in a particular application,for example a molding application requiring that the amount of residualsolvent be less than about 100 parts per million based on the weight ofthe polymer product. In such instances it is possible to further reducethe level of residual solvent by subjecting the polymer product to anadditional extrusion step. Thus, the extruder into which thepolymer-solvent mixture is first introduced may be coupled to a secondextruder, the second extruder being equipped with one or moresubatmospheric or atmospheric vents for the removal of residual solvent.The second extruder may be closely coupled to the initial extruderthereby avoiding any intermediate isolation and re-melting steps. Theuse of a second extruder in this manner is especially beneficial duringoperation at high throughput rates where the residence time of thepolymer in the initial extruder is insufficient to achieve the desiredlow level of residual solvent. The second extruder may be any ventedextruder such as a vented twin-screw counter-rotating extruder, a ventedtwin-screw co-rotating extruder, a vented single-screw extruder, or avented single-screw reciprocating extruder. The term vented extrudermeans an extruder possessing at least one vent, the vent being operatedat atmospheric pressure or subatmospheric pressure. Where the extrudercomprises a plurality of vents, some vents may be operated atatmospheric pressure while others are operated at subatmosphericpressure.

In another embodiment the polymer-solvent mixture is filtered in asolution filtration system prior to its introduction into the extruder.The polymer-solvent mixture may be filtered prior to and/or afterheating or superheating to a temperature greater than the boiling pointof the solvent. A preferred solution filtration system is one that is indirect communication with the extruder via a pressure control valveattached directly to the extruder. A highly preferred solutionfiltration system is an in-line metal filter. Alternatively, theextruder may optionally comprise a melt filtration system for filteringthe polymer melt in the extruder.

The polymer-solvent mixture may comprise a wide variety of polymers.Exemplary polymers include polyetherimides, polycarbonates,polycarbonate esters, poly(arylene ether)s, polyamides, polyarylates,polyesters, polysulfones, polyetherketones, polyimides, olefin polymers,polysiloxanes, poly(alkenyl aromatic)s, and blends comprising at leastone of the foregoing polymers. In instances where two or more polymersare present in the polymer-solvent mixture, the polymer product may be apolymer blend, such as a blend of a polyetherimide and a poly(aryleneether). Other blends may include a polyetherimide and a polycarbonateester. It has been found that the pre-dispersal or pre-dissolution oftwo or more polymers within the polymer-solvent mixture allows for theefficient and uniform distribution of the polymers in the resultingisolated polymer product matrix.

As used herein, the term polymer includes both high molecular weightpolymers, for example bisphenol A polycarbonate having a number averagemolecular weight M_(n) of 10,000 atomic mass units (amu) or more, andrelatively low molecular weight oligomeric materials, for examplebisphenol A polycarbonate having a number average molecular weight ofabout 800 amu. Typically, the polymer-solvent mixture is a productmixture obtained after a polymerization reaction, or polymerderivatization reaction, conducted in a solvent. For example, thepolymer-solvent mixture may be the product of the condensationpolymerization of bisphenol A dianhydride (BPADA) withm-phenylenediamine in the presence of phthalic anhydride chainstopper inODCB, or the polymerization of a bisphenol, such as bisphenol A, withphosgene conducted in a solvent such as methylene chloride. In the firstinstance, a water soluble catalyst is typically employed in thecondensation reaction of BPADA with m-phenylenediamine and phthalicanhydride, and this catalyst can removed prior to any polymer isolationstep. Thus, the product polyetherimide solution in ODCB is washed withwater and the aqueous phase is separated to provide a water washedsolution of polyetherimide in ODCB. In such an instance, the waterwashed solution of polyetherimide in ODCB may serve as thepolymer-solvent mixture which is separated into polymeric and solventcomponents using the method described herein. Similarly, in thepreparation of bisphenol A polycarbonate by reaction of bisphenol A withphosgene in a methylene chloride-water mixture in the presence of aninorganic acid acceptor such as sodium hydroxide, the reaction mixtureupon completion of the polymerization is a two-phase mixture ofpolycarbonate in methylene chloride and brine. The brine layer isseparated and the methylene chloride layer is washed with acid and purewater. The organic layer is then separated from the water layer toprovide a water washed solution of bisphenol A polycarbonate inmethylene chloride. Here again, the water washed solution of bisphenol Apolycarbonate in methylene chloride may serve as the polymer-solventmixture which is separated into polymeric and solvent components usingthe method described herein.

Polymer derivatization reactions carried out in solution are frequentlyemployed by chemists wishing to alter the properties of a particularpolymeric material. For example, polycarbonate prepared by the meltpolymerization of a bisphenol such as bisphenol A with a diarylcarbonate such as diphenyl carbonate may have a significant number ofchain terminating hydroxyl groups. It is frequently desirable to convertsuch hydroxyl groups into other functional groups such as esters byreacting the polycarbonate in solution with an electrophilic reagentsuch as an acid chloride, for example benzoyl chloride. Here, thepolymer is dissolved in a solvent, the reaction with benzoyl chlorideand an acid acceptor such as sodium hydroxide is performed and thereaction mixture is then washed to remove water soluble reagents andbyproducts to provide a polymer-solvent mixture necessitating solventremoval in order to isolate the derivatized polymer. Suchpolymer-solvent mixtures may be separated into polymeric and solventcomponents using the method described herein.

In one embodiment the polymer-solvent mixture comprises a polyetherimidehaving structure I

wherein R¹ and R³ are independently at each occurrence halogen, C₁-C₂₀alkyl, C₆-C₂₀ aryl, C₇-C₂₁ aralkyl, or C₅-C₂₀ cycloalkyl;

-   R² is C₂-C₂₀ alkylene, C₄-C₂₀ arylene, C₅-C₂₀ aralkylene, or C₅-C₂₀    cycloalkylene;-   A¹ and A² are each independently a monocyclic divalent aryl radical,    Y¹ is a bridging radical in which one or two carbon atoms separate    A¹ and A²; and m and n are independently integers from 0 to 3.

Polyetherimides having structure I include polymers prepared bycondensation of bisphenol-A dianhydride (BPADA) with an aromatic diaminesuch as m-phenylenediamine, p-phenylene diamine,bis(4-aminophenyl)methane, bis(4-aminophenyl)ether,hexamethylenediamine; 1,4-cyclohexanediamine and the like.

The methods described herein are particularly well suited to theseparation of polymer-solvent mixtures comprising one or morepolyetherimides having structure I. Because the physical properties,such as color and impact strength, of polyetherimides I may be sensitiveto impurities introduced during manufacture or handling, and because theeffect of such impurities may be exacerbated during solvent removal, oneaspect of the present method demonstrates its applicability to theisolation of polyetherimides prepared via distinctly different chemicalprocesses.

One process for the preparation of polyetherimides having structure I isreferred to as the nitro-displacement process. In the nitro displacementprocess, N-methylphthalimide is nitrated with 99% nitric acid to yield amixture of N-methyl-4-nitrophthalimide (4-NPI) andN-methyl-3-nitrophthalimide (3-NPI). After purification, the mixture,containing approximately 95 parts of 4NPI and 5 parts of 3-NPI, isreacted in toluene with the disodium salt of bisphenol-A (BPA) in thepresence of a phase transfer catalyst. This reaction gives BPA-bisimideand NaNO₂ in what is known as the nitro-displacement step. Afterpurification, the BPA-bisimide is reacted with phthalic anhydride in animide exchange reaction to afford BPA-dianhydride (BPADA), which in turnis reacted with meta-phenylene diamine (MPD) in ortho-dichlorobenzene inan imidization-polymerization step to afford the product polyetherimide.

An alternate chemical route to polyetherimides having structure I is aprocess referred to as the chloro-displacement process. The chlorodisplacement process is illustrated as follows: 4-chloro phthalicanhydride and meta-phenylene diamine are reacted in the presence of acatalytic amount of sodium phenyl phosphinate catalyst to produce thebischlorophthalimide of meta-phenylene diamine (CAS No. 148935-94-8).The bischolorophthalimide is then subjected to polymerization by chlorodisplacement reaction with the disodium salt of BPA in the presence ofhexaethylguanidinium chloride catalyst in ortho-dichlorobenzene oranisole solvent. Alternatively, mixtures of 3-chloro- and4-chlorophthalic anhydride may be employed to provide a mixture ofisomeric bischlorophthalimides which may be polymerized by chlorodisplacement with BPA disodium salt as described above.

Polyetherimides prepared by nitro displacement or chloro displacementprocesses carried out on 4-NPI or bisphthalimide prepared from4-chlorophthalic anhydride possess identical repeat unit structures, andmaterials of similar molecular weight should have essentially the samephysical properties. A mixture of 3-NPI and 4-NPI ultimately affords,via the nitro displacement process, polyetherimide having the samephysical properties as polyetherimide prepared in the chlorodisplacement process from a similarly constituted mixture of 3-chloro-and 4-chlorophthalic anhydride. Because the suite of impurities presentin any polymer depends in part upon the method of its chemicalsynthesis, and because, as noted, the physical properties ofpolyetherimides are sensitive to the presence of impurities, a study wasundertaken to determine whether the present method was applicable to theisolation of polyetherimides prepared by nitro displacement and chlorodisplacement without compromising the physical properties of eithermaterial. It has been found, and is well documented in the examplesdetailed herein, that the method may be applied to the isolation of bothnitro displacement and chloro displacement polyetherimides withoutadversely affecting their physical properties. In some instances, aswhen the polymer contains insoluble particulate material, for example,dissolving the polymer in a solvent such as ODCB and filtering thesolution to remove the insoluble particulate material followed bysolvent removal according to the method allows recovery of polymerphysical properties compromised by the presence of the insolubleparticulate material. This effect of recovering polymer propertiescompromised by the presence of an impurity is observed inpolyetherimides containing insoluble, dark particles (black specks)which are believed to act as stress concentrators during mechanicaltesting (e.g. Dynatup testing) and which negatively impact test scores.

The application of the method to a polymer-solvent mixture effects theseparation of the solvent component from the polymeric component. Thepolymeric component emerging from the extruder is said to bedevolatilized and is frequently referred to as the polymer product. Inone embodiment, the polymer product is found to be substantially free ofsolvent. By substantially free it is meant that the polymer productcontains less than 1000 parts per million (ppm) residual solvent basedon the weight of the sample tested. In some instances the amount ofresidual solvent in the polymer product isolated may exceed 1000 ppm.The concentration of solvent in the final product correlates with theratio between the feed rate and the extruder screw speed, with lowerratios (that is lower rates, or higher screw speeds, or both) leading tolower concentrations of solvent in the polymer product. Theconcentration of the solvent in the polymer product may be adjusted byadjusting the feed rate and/or the extruder screw speed.

In one embodiment, the method provides a polymer product which issubstantially free of solvent and is a polyetherimide having structureI. In an alternate embodiment, the method provides a polymer blend,which is substantially free of solvent. Examples of polymer productblends which are substantially free of solvent include blends containingat least two different polymers selected from the group consisting ofpolycarbonates, polyetherimides, polysulfones, poly(alkenyl aromatic)s,and poly(arylene ether)s.

The polymer-solvent mixtures separated by the method may comprise one ormore solvents. These solvents include halogenated aromatic solvents,halogenated aliphatic solvents, non-halogenated aromatic solvents,non-halogenated aliphatic solvents, and mixtures thereof. Halogenatedaromatic solvents are illustrated by ortho-dichlorobenzene (ODCB),chlorobenzene and the like. Non-halogenated aromatic solvents areillustrated by toluene, xylene, anisole, and the like. Halogenatedaliphatic solvents are illustrated by methylene chloride; chloroform;1,2-dichloroethane; and the like. Non-halogenated aliphatic solvents areillustrated by ethanol, acetone, ethyl acetate, and the like.

In one embodiment, the method may further comprise a compounding step.An additive, a filler, or an additional polymer may be added to thepolymer-solvent mixture via the extruder which further comprises anon-venting side feeder. A non-venting side feeder differs from the sidefeeder mentioned previously in that the non-venting side feeder does notfunction to vent solvent vapors from the extruder. Such an embodiment isillustrated by the case in which an additive, such as a flame retardantor an additional polymer, is preferably introduced at a point along theextruder barrel downstream of most or all vents that are present on theextruder barrel for the removal of solvent. The additive so introducedis mixed by the action of the extruder screws with the partially orfully devolatilized polymer and the product emerges from the extruderdie face as a compounded polymeric material. When preparing compoundedpolymeric materials in this manner it is at times advantageous toprovide for additional extruder barrels and to adapt the screw elementsof the extruder to provide vigorous mixing down stream of the pointalong the barrel at which the additive is introduced. The extruder maycomprise a vent downstream of the non-venting side feeder to removevolatiles still remaining, or that may have been produced by the sidefeeder addition of the additive, filler, and/or additional polymer tothe extruder.

As mentioned above, the additional polymer introduced in the compoundingstep may include a polyetherimide, a polycarbonate, a polycarbonateester, a poly(arylene ether), a polyamide, a polyarylate, a polyester, apolysulfone, a polyetherketone, a polyimide, an olefin polymer, apolysiloxane, a poly(alkenyl aromatic), and a combination comprising atleast one of the foregoing polymers, and the like.

Non-limiting examples of fillers include silica powder, such as fusedand fumed silicas and crystalline silica; talc; glass fibers; carbonblack; conductive fillers; carbon nanotubes; nanoclays; organoclays; acombination comprising at least one of the foregoing fillers; and thelike.

The amount of filler present in the polymer can range anywhere of about0 to about 50 weight percent based on the total weight of thecomposition, preferably from about 0 to about 20 weight percent thereof.

The additives include, but are not limited to, colorants such aspigments or dyes, UV stabilizers, antioxidants, heat stabilizers,foaming agents, and mold release agents. Where the additive is one ormore conventional additives, the product may comprise about 0.0001 toabout 10 weight percent of the desired additives, preferably about0.0001 to about 1 weight percent of the desired additives.

In another embodiment, the polymer-solvent mixture may further compriseat least one filler and/or at least one additive prior to itsintroduction into the extruder. It has been found that the pre-dispersalof filler into the polymer-solvent mixture allows for the efficient anduniform distribution of the filler in the resulting isolated polymerproduct matrix. The lower viscosity of the polymer-solvent mixtureallows for efficient mixing of the filler and polymer with a minimizedusage of energy as compared to compounding the filler and polymer in anextruder or similar device. Accordingly, a one-step process ofcompounding/isolation/devolatilization is disclosed to provide filledpolymer product without the need for the usual remelting and compoundingof the polymer and filler after the isolation step has been performed. Afurther advantage of adding the filler to the polymer-solvent mixturerather than compounding it in an extruder is to minimize the heathistory of the polymer.

In one embodiment, the polymer-solvent mixture further comprises aliquid crystalline polymer, such as liquid crystalline polyester andcopolyesters. Suitable liquid crystalline polymers are described in U.S.Pat. Nos. 5,324,795; 4,161,470; and 4,664,972.

The fillers and additives that may be dispersed in the polymer-solventmixture may be any of those listed for the additional compounding stepabove.

Polymeric materials isolated according to the methods described hereinmay be transformed into useful articles directly, or may be blended withone or more additional polymers or polymer additives and subjected toinjection molding, compression molding, extrusion methods, solutioncasting methods, and like techniques to provide useful articles.Injection molding is frequently the more preferred method of forming theuseful articles.

In one embodiment, a method for separating a polymer from a solventcomprises introducing a superheated polymer-solvent mixture via apressure control valve located on a barrel of an extruder, wherein theextruder comprises an upstream vent, a downstream vent, and a sidefeeder, wherein the side feeder comprises a side feeder vent and theupstream vent and the side-feeder vent are operated at about atmosphericpressure and the downstream vent is operated at subatmospheric pressure;removing solvent from the superheated polymer-solvent mixture via theupstream vent, the downstream vent and the side feeder vent; andisolating a polymer product from the polymer solvent mixture; whereinthe polymer-solvent mixture comprises a polymer and a solvent.

In one embodiment, a method for separating a polymer from a solventcomprises introducing a superheated polymer-solvent mixture via apressure control valve located on a side feeder attached to an extruder,wherein the extruder comprises a downstream vent, wherein the sidefeeder comprises a side feeder vent, wherein the pressure control valveis located between the extruder and the side feeder vent; removingsolvent from the superheated polymer-solvent mixture via the downstreamvent and the side feeder vent; and isolating a polymer product from thepolymer solvent mixture; wherein the polymer-solvent mixture comprises apolymer and a solvent.

In one embodiment, a system for separating a polymer from a solvent, thesystem comprising a means for heating a polymer-solvent mixture,preferably to provide a superheated polymer-solvent mixture; an extruderin communication with the means for heating a polymer solvent mixture,the communication being via at least one feed inlet, preferably apressure control valve through which a polymer-solvent mixture may beintroduced into the extruder, the extruder being equipped with at leastone upstream vent adapted for operation at atmospheric or subatmosphericpressure, and at least one down stream vent adapted for operation atsubatmospheric pressure; and optionally at least one side feeder incommunication with the extruder, the side feeder being equipped with atleast one vent adapted for operation at atmospheric or subatmosphericpressure and optionally at least one pressure control valve throughwhich the polymer-solvent mixture may be introduced into the extrudervia the side feeder. As an example of what is meant by the expressionsin communication with or to communicate with, the side feeder is said tobe in communication with or to communicate with the extruder because thebarrel of the side feeder is understood to intersect the barrel of theextruder allowing for the passage of solvent vapor generated in theextruder barrel outwards along the side feeder barrel out through thevent of the side feeder.

Means for heating a polymer-solvent mixture to provide a heated orsuperheated polymer-solvent mixture include heated feed tanks, heatexchangers, reaction vessels, all of which may or may not bepressurized, extruders, and the like.

The extruder in communication with the means for heating a polymersolvent mixture may be a twin-screw counter-rotating extruder, atwin-screw co-rotating extruder, a single-screw extruder, or asingle-screw reciprocating extruder.

FIGS. 1 and 2 illustrate two exemplary embodiments of the disclosedsystem and method. FIG. 1 illustrates a system and a method comprising anitrogen-pressurized, heated feed tank (1) for supplying apolymer-solvent mixture, a gear pump (2) for pumping the mixture thougha flow meter (3) and heat exchanger (4). The heat exchanger providesheat (5) to provide a superheated polymer-solvent mixture (6) which isforced by the action of the gear pump through in-line filters (7) toremove particulate impurities from the superheated polymer-solventmixture which passes through a pressure control valve (8) and a shortconnecting pipe (9) to the feed zone of a twin-screw extruder (10)having screw design (24). Extruder (10) is equipped with a side feeder(11) and nitrogen gas inlets (12) and (13). Upstream vent (14) and aside feeder vent (15) for removing solvent vapors (18) are located onbarrel 1 (16), and the side feeder (11), respectively. The escapingsolvent vapors (18) are captured in a solvent vapor manifold (19)connected to a condenser (20) where heat (5) is removed and solvent (21)is recovered. Downstream of barrel 4 (17) the extruder screw elementsare configured to provide melt seals (29) in barrel 5 (23) and barrel 8(30) respectively. Downstream vents (22), (26), (27) and (31) providefor the removal of solvent not removed through the upstream vents.Solvent vapors (18) and (32) are condensed and recovered at condensers(20), (33) and (34). The polymer product (35) emerges from the extruderfor pelletization and further use.

FIG. 2 illustrates a portion of the system comprising a twin-screwextruder (36), side feeders (37) and (38), a feed inlet (39) comprisinga pressure control valve, upstream vent (40), side feeder vents (50)located on the side feeders, kneading blocks (41) adapted for capturingsolid polymer entrained by escaping solvent vapor, side feeder conveyingscrew elements (42) which provide for the transfer of polymer depositedin the side feeder to the screws of the twin-screw extruder, (43), (45)and (46) screw elements providing melt seals, and downstream vents (44),(47), (48) and (51) providing for removal of additional solvent.

In one embodiment additional precautions may be taken to exclude oxygenfrom the extruder and from contact with the hot polymer as it emergesfrom the extruder dieface. Such precautions may assist in preventingdiscoloration of the polymer product, especially when the polymerproduct is known to darken or otherwise degrade at high temperature inthe presence of oxygen. For example, polyetherimides and poly(phenyleneethers) are known to be sensitive to oxygen at high temperature anddarken measurably when heated in the presence of oxygen. Steps which maybe taken in order to minimize the concentration of oxygen in theextruder, or to minimize the exposure of the hot polymer emerging fromthe extruder dieface to oxygen include: wrapping external parts of theextruder with cladding and supplying the cladding with a positivepressure of nitrogen, enclosing with a housing supplied with a positivepressure of inert gas those sections of the extruder subject to theentry of oxygen due to the action of vacuum the vents, enclosing theentire extruder in an enclosure supplied with a positive pressure ofnitrogen, and the like. Additionally, steps may be taken to degas thepolymer-solvent mixture prior to its introduction into the extruder.Degassing may be effected in a variety of ways, for example sparging thepolymer-solvent mixture with an inert gas and thereafter maintaining apositive pressure of an inert gas in the vessel holding thepolymer-solvent mixture.

EXAMPLES

The following examples are set forth to provide those of ordinary skillin the art with a detailed description of how the methods claimed hereinare carried out and evaluated, and are not intended to limit the scopeof what the inventors regard as their invention. Unless indicatedotherwise, parts are by weight and temperature is in ° C.

Molecular weights are reported as number average (M_(n)) or weightaverage (M_(w)) molecular weight and were determined by gel permeationchromatography (GPC) using polystyrene (PS) molecular weight standards.Example 5 provides a general illustration of the method. ULTEM® 1010polyetherimide is commercially available from GE Plastics, MT Vernon,Ind. Throughout the Examples and the Comparative Examples the systemused to effect-polymer-solvent separation comprised a co-rotating,intermeshing (i.e. self wiping) twin-screw extruder.

Examples 1-4 and 6-7 were carried out using the same extruderdevolatilization system and same 30 percent solution of polyetherimidein ODCB described in Example 5 below. Variations in the conditionsemployed are provided in Table 1.

Example 5

A polymer-solvent mixture containing about 30 percent by weightpolyetherimide (ULTEM® 1010 polyetherimide; prepared by thenitro-displacement process) and about 70 percent by weightortho-dichlorobenzene (ODCB) was prepared and heated to a temperature of156° C. in a feed tank under a nitrogen atmosphere (50-60 psig N₂ or3.5-4.2 kilogram-force per square centimeter (kgf/cm²)). Nitrogen wasused to provide enough pressure to feed the pump head of the gear pump.Additionally the nitrogen is believed to have inhibited degradation ofthe polymer in the solution. Air is not used because it may causecoloration and molecular weight change when the polymer-solvent mixturecomprises air sensitive polymers such as polyetherimides. Additionally,the polymer-solvent mixture comprised the commercial stabilizersIRGAFOS® 168 (0.12 percent by weight based on the weight of the polymer)and IRGANOX® 1010 (0.10 percent by weight based on the weight of thepolymer).

The solution was transferred from the heated feed tank by means of agear pump at a rate of about 50 pounds of solution per hour (22.7kilogram per hour (kg/hr)) to a heat exchanger maintained at about 288°C. The polymer-solvent mixture emerged from the heat exchanger at atemperature of about 261° C. and was fed through a pressure controlvalve plumbed into the upstream edge of barrel 3 of a 10-barrel, 25 mmdiameter, co-rotating, intermeshing twin-screw extruder having a lengthto diameter ratio (L/D) of about 40. The cracking pressure of thepressure release valve was electronically controlled such that a steadystream of the superheated polymer-solvent mixture was introduced intothe extruder. In this example (Example 5) the temperature of thepolymer-solvent mixture as it was introduced into the extruder throughthe pressure control valve was 229° C., 49° C. higher than the boilingpoint of ODCB (boiling point 180° C.). The pressure control valve wasoperated with the cracking pressure set at about 86 psi (6.0 kgf/cm²).The valve was 19 percent open. The extruder was operated at a screwspeed of about 391 rpm, at about 45 percent of the maximum availabletorque, and at a die pressure of about 177 psi (12.4 kgf/cm²). Themeasured extruder barrel temperatures were 330, 340, 339, 348, 332, and340° C. for the six temperature-controlled zones in the extruder.

The extruder was equipped with a closed chamber upstream of barrel 1,the closed chamber having a nitrogen line adapted for the controlledintroduction of nitrogen gas before and during the solvent removalprocess. The extruder was further equipped at barrel two with a sidefeeder positioned orthogonal to the barrel of the extruder. The sidefeeder was not heated, had an L/D of about 10, and comprised two screwsconsisting of forward conveying elements only. At the end most distantfrom the extruder barrel, the side feeder was equipped with a singleatmospheric vent (V1). The conveying elements of the screws of the sidefeeder were configured to convey toward the extruder and away from theside feeder vent. The extruder was further equipped with two additionalatmospheric vents at barrel 1 (V2) and barrel 4 (V3) and vacuum vents(vents operated at subatmospheric pressure) at barrel 6 (V4) and barrel8 (V5). The three atmospheric vents, two on the extruder and one on theside feeder, were each connected to a solvent removal and recoverymanifold comprising solvent vapor removal lines, a condenser, and liquidsolvent receiving vessel. The vacuum vents were similarly adapted forsolvent recovery. Vents V2 and V5 were equipped with Type A vent insertswhile the vents V3 and V4 were equipped with Type C and Type B ventinserts respectively. Vent inserts are available from the Werner &Pfleiderer Company. Vent inserts differ in the cross sectional areaavailable for the solvent vapors to escape the extruder: Type A insertsare the most restrictive (smallest cross section) and Type C are themost open (largest cross section). The vent on the side feeder V1 wasnot equipped with a vent insert.

The extruder screw elements consisted of both conveying elements andkneading elements. All of the conveying elements in both the extruderand the side feeder were forward flighted conveying elements. Kneadingelements used included neutral, forward flighted and rearward flightedkneading elements depending on function. In barrels 2 and 3 of theextruder, kneading blocks consisting of forward and neutral flightedkneading elements were employed. Substantially all, about 95 percent ormore, of the solvent was removed through the atmospheric vents.

That substantially all of the solvent was removed through theatmospheric vents (V1, V2, and V3) was determined as follows. The totalamount of solvent collected from the atmospheric vents was measuredafter the experiments constituting Examples 1-7 were completed. Thetotal amount of polymer-solvent mixture fed in Examples 1-7 was about140 pounds (63.5 kg) comprising about 42 pounds (19.1 kg) of polymer andabout 98 pounds (44.5 kg) of solvent. Of this, 97 pounds (44 kg) ofsolvent was recovered from the receiving vessel attached to theatmospheric vents (V1, V2 and V3), 0.8 pounds (0.36 kg) of solvent wasrecovered from a receiver attached to vacuum vent (V4), and 0.4 pounds(0.18 kg) of solvent was recovered from a receiver attached to vacuumvent (V5). Thus, about 98.5% of the total amount of solvent was removedthrough the atmospheric vents (V1, V2 and V3).

The extruder screws were equipped with melt seals consisting of kneadingblocks made up of rearward flighted kneading elements. The melt sealswere located at barrels 5, and 7. The vacuum vents were locateddownstream of the melt seals on barrel 6 and barrel 8 and were operatedat vacuum levels of about 28 inches (about 711.2 millimeters (mm)) ofmercury (a vacuum guage indicating full vacuum, or zero absolutepressure, would read about 30 inches (about 762.0 mm) of mercury (Hg)).The devolatilized polyetherimide, which emerged from the die face (melttemperature about 389° C.) of the extruder was stranded and pelletized.The pelletized polyetherimide (approximately 6 pounds or 2.7 kg) wasfound to contain about 334 ppm residual ODCB.

Data for Examples 1-7 are gathered in Table 1. In the column headed“Pressure (mm Hg)” values for the vacuum measured at vacuum vents V4 andV5 are given in millimeters of mercury. “T Feed after Heat Exch. (° C.)”indicates the temperature of the polymer-solvent mixture after passagethrough the heat exchanger. “P-valve (° C.)” indicates the temperatureof the polymer-solvent mixture at the pressure control valve. “CrackingPressure (kgf/cm²)/% Open” provides the cracking pressure of thepressure control valve and the extent to which the pressure controlvalve is open, 100 meaning the valve is fully open and 20 meaning thevalve opening cross sectional area is 20 percent of the opening crosssectional area of fully open valve. “Residual ODCB by GC (ppm)” providesthe amount of residual ODCB in parts per million (ppm) remaining in thedevolatilized polymer following pelletization and was determined by gaschromatography.

TABLE 1 Vacuum Mass Screw Die (mm Hg) Flow Torque Melt speed PressureExample V4 V5 (kg/hr) (%) (° C.) (rpm) (kgf/cm²) Barrel Temperatures (°C.) 1 304.8 711.2 22.7 38 389 385 17.6 335/310/339/350/333/351 2 431.8711.2 22.7 44 387 385 14.7 320/330/340/347/330/340 3 304.8 711.2 22.7 44387 385 13.6 321/327/342/348/330/340 4 431.8 711.2 22.7 44 387 385 12.8327/329/339/351/330/340 5 711.2 711.2 22.7 45 389 391 12.4330/340/339/348/332/340 6 711.2 711.2 34.0 47 397 450 14.7330/319/340/349/335/340 7 711.2 711.2 43.5 48 404 498 16.6327/307/336/354/342/340 T of Cracking Heating Oil T feed after Pressurefor Heat Residual Feed Tank Heat Exch. (kgf/cm²)/% Exchanger ODCB byExample (° C.) (° C.) P-valve (° C.) Open (° C.) GC (ppm) 1 159 191 1830.35/100 598 2 159 232 189–195 6.2/20 254 560 3 160 250 205 6.3/20 288434 4 156 267 221 6.6/20 288 587 5 156 261 229 6.0/19 288 334 6 157 264225 6.0/20 288 604 7 158 260 215 6.8/20 969

The data in Table 1 illustrate the effectiveness of the method forseparating a polymer from a large amount of solvent in a single step andproviding a polymetric material, which is substantially free of solvent.

Examples 8-11 were carried out using the same extruder devolatilizationsystem configured as in Example 5 using a freshly preparedpolymer-solvent mixture identical to that employed in Example 5. Datafor Examples 8-11 are gathered in Table 2 and illustrate the limits onthe rate at which the polymer-solvent mixture may be introduced into theextruder. At the high feed rates employed in Examples 8-11 the separatedpolymer retains a higher level of solvent than was observed in Examples1-7. The column headings in Table 2 have the same meanings as those ofTable 1.

TABLE 2 Vacuum Screw Die (mm Hg) Mass Torque speed Pressure BarrelExample V4 V5 Flow (kg/hr) (%) Melt (° C.) (rpm) (kgf/cm²) Temperatures(° C.)  8 711.2 711.2 47.6 53 395 433 23.7 317/323/323/345/329/329  9711.2 711.2 47.6 52 398 471 22.2 315/340/328/350/331/330 10 711.2 711.249.9 54 397 471 22.8 317/340/336/346/330/330 11 711.2 711.2 68.0 55 409600 21.7 319/336/338/347/334/331 T feed after Residual Feed Tank HeatExch. P-valve ODCB by Solution YI Example (° C.) (° C.) (° C.) GC (ppm)(Corrected)  8 161 252 203 2236 24.6  9 161 270 217.5 1420 24.7 10 165267 221 1956 23.3 11 167 247 208 2514 23.2

Examples 12-21 were carried out using the same extruder devolatilizationsystem configured as in Example 5 (but including an in-line sinteredmetal filter upstream of the pressure control valve) using two freshlyprepared polymer-solvent mixtures comprising 30 percent by weightpolyetherimide in ODCB. Two different batches of polyetherimide preparedby the nitro displacement process were employed. The polyetherimide usedto prepare the polymer-solvent mixture employed in Examples 12-18 and20-21 was prepared in a pilot plant from the same chemical components(BPADA, m-phenylenediamine, and phthalic anhydride chainstopper), in thesame proportions, as are used in the manufacture of commerciallyavailable ULTEM® polyetherimide. This pilot plant material hadM_(w)=42,590 amu, M_(n)=18,270 amu, and a polydispersity (PI) value of2.33. Commercially available ULTEM® polyetherimide was used in Example19 and had M_(w)=44,250 amu, M_(n)=19,420 amu, and a polydispersityvalue of 2.28. Thus, each of the two polyetherimides employed wasessentially identical in terms of chemical composition and molecularweight. The pilot plant material differed in one important respect fromthe commercial polyetherimide. The pilot plant material without beingsubjected to dissolution in ODCB and solvent removal exhibited a DynatupEnergy to maximum load value at 100° C. of 33.99 ft-lb (46.08 Joule (J))(standard deviation 18.59 ft-lb (25.20 J)), and was judged to be about40 percent ductile. In the same test the commercial grade ULTEM®polyetherimide displayed a value of 53.43 ft-lb (72.44 J) (standarddeviation 2.52 ft-lb (3.42 J)) and was 100 percent ductile. Thissomewhat poor ductility was attributable to the presence of particulatematerial (specks) in the pilot plant material. It is believed that theseparticles reduce the impact strength of a molded part by acting asstress concentrators when a plaque molded from the particle containingresin is impacted by a moving plunger in the Dynatup test. As shown bythe data presented in Table 3, the ductility loss attributable to thepresence of the specks in the pilot plant material could be recoveredupon filtration of the polymer-solvent mixture prepared from the pilotplant material through a sintered metal filter (PALL 13-micron Filter)positioned between the heat exchanger and the pressure control valve.

Each of the two polymer-solvent mixtures comprised the commercialstabilizers IRGAFOS® 168 (0.12 percent by weight based on the weight ofthe polymer) and IRGANOX® 1010 (0.10 percent by weight based on theweight of the polymer). Some 400 pounds (181 kg) of the polymer-solventmixture prepared from pilot plant polyetherimide was extruded in each ofExamples 12-18 and 20-21. In Example 19 about 100 pounds (45.4 kg) ofpolymer-solvent mixture prepared from commercial ULTEM® polyetherimidewas extruded. Data for Examples 12-21 are gathered in Table 3 andillustrate that the polymer-solvent mixture may be fed at high rates(about 75 pounds per hour or 34.0 kg/hr) while still achieving very lowlevels of residual solvent in the recovered polymer. Thus, the polymeremerging from the extruder was pelletized and the pellets were found tobe substantially free (<1000 ppm) of ODCB. In the experiment forming thebasis of Example 19, the extruded, pelletized product was sampled fourtimes during the experiment to determine the level of residual ODCB,hence the presence of multiple values of “Residual ODCB by GC (ppm)”given in Example 19. Additionally, the extruded, pelletized product inExample 19 was sampled twice for Dynatup energy testing. All Dynatuptests were conducted using the standard ASTM method D3763 (conducted at100° C.) on plaques molded from the extruded, pelletized productpolyetherimide. Percent ductility was determined by examination of thefailure mode of the part in the Dynatup test. Failure was judged to beeither ductile failure or nonductile failure. Any failure in which theplaque broke into two or more parts was judged to be nonductile failure.A value of “Ten/100” under the heading “No. Samples/Ductile(%)”indicates that of the ten plaques tested in the Dynatup test, all tenplaques (or 100%) failed in a ductile manner. The column headings inTable 3 common to Tables 1 and 2 have the same meanings as those ofTables 1 and 2. The column heading “Dynatup Energy @ Max. Load/St. Dev.(J) @100C” gives the average Dynatup test value in joules and standarddeviation obtained from the testing of ten molded plaques prepared fromthe polyetherimide isolated.

TABLE 3 Vacuum Screw Die (mm Hg) Mass Torque speed Pressure BarrelExample V4 V5 Flow (kg/hr) (%) Melt (° C.) (rpm) (kgf/cm²) Temperatures(° C.) 12 711.2 711.2 34.0 48 392 449 24.0 308/324/357/331/329/329 13711.2 711.2 34.0 49 393 449 21.9 310/265/335/354/331/330 14 711.2 711.233.6 48 394 453 23.6 324/289/361/351/331/330 15 711.2 711.2 33.6 49 394453 21.7 326/266/348/351/330/330 16 711.2 711.2 34.0 49 394 453 24.3328/303/350/350/330/330 17 711.2 711.2 34.0 49 394 453 22.4331/281/350/351/330/330 18 711.2 711.2 34.0 50 394 453 22.7330/303/347/354/331/330 19 711.2 711.2 34.0 52 400 453 24.2331/336/351/356/338/330 20 711.2 711.2 34.0 46 389 400 25.5337/320/391/357/324/330 21 711.2 711.2 34.0 48 388 400 23.5336/318/365/348/323/330 T feed Dynatup after Energy @ Feed Heat CrackingMax. Load/ Number of Tank Exch. P-valve Pressure(kgf/cm²)/ Residual ODCBSt. Dev. (J) Samples Tested/ Example (° C.) (° C.) (° C.) % Open by GC(ppm) @100 C. Ductile (%) 12 153 255 236 4.1/21   828 63.2/7.1 Ten/90 13159 260 235 4.1/19.5 636 66.8/3.1 Ten/100 14 168 264 247 3.9/19.5 45464.9/10.8 Ten/80 15 168 279 250 4.1/19.5 358 55.3/19.0 Ten/90 16 169 285249 4.1/19.5 370 63.9/1.1 Ten/100 17 170 284 251 4.0/19.5 411 64.0/0.8Ten/100 18 154 282 244 3.4/25   19 159 282 244 3.4/25   306/238/520/21969.7/2.0 Ten/100 67.0/0.7 Ten/100 20 155 282 242 3.3/25   229 64.3/0.4Ten/100 21 156 282 242 3.3/25   341 56.5/17.9 Ten/80

In Examples 22-31 the extruder devolatilization system was configured asin Example 5 with the following modifications: A PALL 13-micron sinteredmetal filter was placed in the feed line between the heat exchanger andthe pressure control valve (upstream of the pressure control valve), andthe ten barrel twin-screw extruder was adapted to perform as an 8 barrelextruder. The following changes were made to the extruder. Barrels 1 and2 were so-called blind barrels fitted with dummy space filling screwelements; the pressure control valve was attached to the extruder on thedownstream edge of barrel 4; the side feeder was attached to theextruder at barrel 4; the atmospheric vents (V1, V2 and V3) were locatedon the side feeder as in Example 5, and on barrels 3 and 5 respectively;and the vacuum vents (V4) and (V5) were located on barrels 7 and 9respectively. Type C inserts were used in vents (V2-V5). No vent insertwas used in (V1), the atmospheric vent on the side feeder. As inExamples 1-21 the extruder screw elements included conveying elementsunder all vents, melt seal-forming left handed kneading blocks justupstream of each vacuum vent and narrow-disk right handed kneadingblocks at the side feeder. Two polymer-solvent mixtures were employed.The first was used in Examples 22-26 and comprised a 30 percent solutionof commercial ULTEM® 1010 polyetherimide in ODCB stabilized as inExample 5. ULTEM® 1010 polyetherimide was prepared using the nitrodisplacement process. The second polymer-solvent mixture was used inExamples 27-31 and was prepared using polyetherimide having a chemicalstructure essentially identical to that of ULTEM® polyetherimide, butprepared by the chloro displacement method. This second polymer-solventmixture contained 30 percent by weight of chloro displacementpolyetherimide in ODCB and was stabilized with IRGAFOS® 168 and IRGANOX®1010 as in Example 5.

TABLE 4 Vacuum Mass Screw Die (mm Hg) Flow Torque speed Pressure BarrelExample V4 V5 (kg/hr) (%) Melt (° C.) (rpm) (kgf/cm²) Temperatures (°C.) 22 711.2 711.2 31.8 45 365 475 7.8 337/352/352/344/351/350/345/33623 711.2 711.2 31.8 46 364 475 7.4 333/348/350/350/350/349/344/335 24711.2 711.2 31.8 45 365 476 8.6 336/350/350/349/350/350/345/335 25 711.2711.2 31.8 45 366 476 9.8 336/350/350/350/350/350/346/335 26 711.2 711.231.8 45 366 476 8.9 336/350/350/350/350/350/346/335 27 711.2 711.2 31.344 366 475 9.9 345/351/347/342/349/351/345/336 28 711.2 711.2 29.0 47363 485 11.0  341/352/350/341/339/331/331/334 29 711.2 711.2 29.0 47 362485 11.2  336/350/350/340/337/329/329/335 30 711.2 711.2 29.0 47 362 48411.7  334/350/350/340/336/329/330/335 31 711.2 711.2 29.0 48 362 485 9.9333/350/350/340/337/330/331/335 T feed after Cracking Residual DynatupEnergy Number of Feed Heat Pressure ODCB @ Max. Load/ Samples Tank Exch.P-valve (kgf/cm²)/% by GC St. Dev. (J) Tested/ Example (° C.) (° C.) (°C.) Open (ppm) @100 C. Ductile (%) 22 167 275 239 6.7/34 27.1/21.7Ten/10 23 168 269 243 5.4/34 24 160 278 244 7.4/33 64.3/7.3 Ten/100 25162 275 245 6.5/33 26 164 275 246 6.8/33 926 64.4/2.4 Ten/100 27 155 253231 5.1/35 865 56.0/20.6 Ten/70 28 157 272 242 7.2/31 802 46.7/27.2Ten/60 29 157 273 245 6.7/31 754 64.4/10.3^(a) Ten/100^(a) 30 159 271246 6.5/31 956 31 162 269 246 6.6/31 — — — ^(a)Measured on a compositesample prepared from material isolated in Examples 29 & 30

The data in Table 4 demonstrate that at moderately high feed rates(64-70 pounds of polymer-solvent mixture per hour or 29.0-31.8 kg/hr)product polyimide was obtained which was substantially free of residualODCB solvent. In Examples 29 and 30 the chloro-displacementpolyetherimide isolated showed both excellent ductility and wassubstantially free of solvent (<1000 ppm). Loss of ductility in Examples27 and 28 is believed to have been due to the accretion and charring ofsmall amounts of polymer at the vent openings during runs Examples 22-26which gradually became dislodged as a result of the changeover to thesecond polymer-solvent mixture used in Examples 27-31. In one embodimentthe extruder is equipped with a melt filter in order to minimize theeffects of any such accretion and charring on the properties of thepolymer product. The data given in Table 4 demonstrate that the methodis applicable to polyetherimide prepared using either the nitrodisplacement or chloro displacement process without negatively affectingproduct quality. Moreover, using the 8-barrel extruder as practiced inExamples 22-31, the polymer-solvent mixture may be separated at lowermelt temperature (about 365° C.) compared with melt temperaturesobserved when a 10-barrrel extruder is employed (385-405° C.) withoutincreasing the solvent level in the polymer product above 1000 ppm.

Examples 32-37 (Table 5) were run using different feed rates, barreltemperatures and screw speeds on the extruder devolatilization systemused in Examples 22-31. The polymer-solvent mixture employed was a 30percent by weight solution of commercial ULTEM® 1010 polyetherimide inODCB stabilized with IRGAFOS® 168 and IRGANOX® 1010 as in Example 5. Inthe experiment comprising Examples 32-37 about 180 pounds (81.6 kg) ofpolymer-solvent mixture was devolatilized, the feed rate gradually beingincreased to a maximum rate in Example 35 of 105 pounds per hour (47.6kg/hr). At this maximum rate, the atmospheric vent at barrel 5 (V3)plugged. Thereafter the feed rate was lowered and the data for Examples36 and 37 collected. In Example 37 all of the extruder barreltemperature controllers (heating and cooling) were turned off tosimulate performance under adiabatic conditions. In Example 33 thethroughput rate was increased 65 to 85 pounds per hour (29.5 to 38.6kg/hr). Under the conditions indicated (melt temperature about 372° C.and a screw speed of about 500 rpm) the polymer product while containingonly a small amount of residual ODCB solvent, contained more than themaximum value targeted in the experiment, 1000 ppm. In Example 34 it wasshown that by adjusting the extruder barrel temperature and the screwspeed upward the amount of residual ODCB in the polymer product could bebrought to under 500 ppm. Even at the highest throughput rateachievable, Example 35, the amount of residual solvent present in thepolymer product could be maintained at a level under 1000 ppm. Example36 was run to equilibrate the system following Example 35. Example 37demonstrates that the method may be carried out using an extruderoperated under adiabatic conditions and still provide product which issubstantially free of solvent.

TABLE 5 Vacuum Screw Die (mm Hg) Mass Torque speed Pressure BarrelExample V4 V5 Flow (kg/hr) (%) Melt (° C.) (rpm) (kgf/cm²) Temperatures(° C.) 32 711.2 711.2 29.5 45 366 452 6.8328/350/351/349/373/342/332/351 33 711.2 711.2 38.6 47 372 500 8.5322/348/351/343/352/346/340/350 34 711.2 711.2 38.6 43 411 750 1.8331/381/374/357/377/378/379/352 35 711.2 711.2 47.6 43 413 750 5.1331/378/378/351/375/380/379/351 36 711.2 711.2 29.9 41 393 500 1.9333/374/376/369/379/370/365/348 37 711.2 711.2 29.9 43 385 505 2.4272/310/298/297/354/364/354/350 Cracking T feed after Pressure Residualo- Feed Tank Heat Exch. P-valve (kgf/cm²)/% DCB by GC Example (° C.) (°C.) (° C.) Open (ppm) 32 153 262 238 6.2/45 876 33 154 278 242 8.4/451478  34 156 276 240 8.6/44 479 35 160 269 240 8.8/44 833 36 161 278 2378.2/43 770 37 163 276 238 7.6/43 861

Examples 38-45 illustrate the system used to perform extruderdevolatilization of polymer-solvent mixtures comprises a 10 barrel, 25mm diameter, co-rating, intermeshing twin-screw extruder having a lengthto diameter ratio (L/D) of 40, a side feeder having an L/D of 10attached to barrel 2 of the extruder, and six vents (V1-V6) arrayed onthe extruder and the side feeder. Vents (V1), (V2), and (V3) wereatmospheric vents and were located on the side feeder, barrel 1, andbarrel 4 respectively. Atmospheric vents (V1-V3) were connected as inExample 5 to a solvent recovery system to which a very slight vacuum(about 1 inch of mercury (about 25.4 mm Hg)) was applied in order toenhance solvent removal through the upstream vents, (V1-V3). Vents (V4),(V5) and (V6) were vacuum vents and were attached to the extruder atbarrel 5, barrel 7 and barrel 9 respectively. Vacuum vents (V4), and(V5) and (V6) were connected to two solvent recovery systems independentof that used for the atmospheric vents (V1-V3). Vents (V3-V6) comprisedType C vent inserts. No vent inserts were used in vents (V1) and (V2).The polymer-solvent mixture was introduced into the extruder through apressure control valve located on the downstream edge of barrel 2. Thescrew design was essentially the same as that used in the previousExamples. Conveying elements were located under the pressure controlvalve and under all vents, left-handed kneading blocks were located justupstream of vacuum vents (V4) and (V6) to provide melt seals upstream ofvacuum vents (V4) and (V6), and forward and neutral kneading blocks werelocated in barrels 2 and 3. As in Example 5, the system comprised aheated feed tank pressurized with nitrogen gas, and a gear pump used totransfer the polymer-solvent mixture from the feed tank, through a heatexchanger and a pressure control valve attached to the extruder.Additionally, the system comprised a pair of in-line sintered metalfilters (PALL 13 micron filters) operated in parallel, the filters beingpositioned between the heat exchanger and the pressure control valve. InExamples 38-45 extruder temperature control was aided by alternatelyheating and air cooling the extruder barrel in order to simulateisothermal conditions. The extruder was adapted for the introduction ofnitrogen gas as described in Example 5. Nitrogen gas was bled into theextruder during all runs.

In Examples 38, 39, 44 and 45 the polymer-solvent mixtures were 30percent by weight solutions of ULTEM® 1010 polyetherimide in ODCB, thesolutions being stabilized as in Example 5. The polymer solvent mixturesused in Examples 44 and 45 contained, in addition, DOVERPHOS® F2028(0.10 weight percent based on the weight of polymer). Thepolymer-solvent mixture employed in Examples 40-43 was an ODCB solutionof polyetherimide prepared by the chloro displacement process, thepolyetherimide having a structure essentially identical to the ULTEM®1010 polyetherimide employed in Examples 38, 39, 44 and 45, except thatthe ratios of 3-substituted and 4-substituted imide groups variedslightly. The chloro displacement polyetherimide isolated in Examples40-43 was prepared starting with a 90:10 mixture of 4-chloro- and3-chlorophthalic anhydride. The polymer-solvent mixture used in Examples40-43 was about 25 percent by weight polyetherimide in ODCB and wasstabilized as in Example 5.

TABLE 6 Vacuum Mass Screw Die (mm Hg) Flow Torque speed Pressure BarrelExample V4 V5 V6 (kg/hr) (%) Melt (° C.) (rpm) (kgf/cm²) Temperatures (°C.) 38 711.2 711.2 711.2 30.4 48 368 450 4.6342/327/350/350/351/356/347/350 39 711.2 711.2 711.2 30.4 49 361 400 8.0356/330/350/350/350/350/345/335 40 711.2 711.2 711.2 27.7 49 369 400 6.3342/325/346/352/349/355/340/351 41 711.2 711.2 711.2 29.5 51 361 400 9.9365/335/351/351/345/349/342/335 42 711.2 711.2 711.2 29.5 50 360 40011.3  354/331/346/350/343/350/346/336 43 711.2 711.2 711.2 29.5 49 363400 9.4 352/333/350/352/349/354/351/336 44 711.2 711.2 711.2 29.9 52 362430 6.9 347/334/352/352/346/350/344/335 45 711.2 711.2 711.2 29.9 50 364430 7.7 343/331/351/350/347/350/349/335 T feed Dynatup after CrackingEnergy @ Number of Feed Heat Pressure Residual Max. Load/ Samples TankExch. P-valve (kgf/cm²)/% ODCB by St. Dev. (J) Tested/ Example (° C.) (°C.) (° C.) Open GC (ppm) @100 C. Ductile (%) 38 161 269 258 6.4/15 29367.1/11.1 Ten/90 39 161 270 258 6.7/14 369 66.4/1.4 Ten/100 40 139 265251 6.8/21 432^(a) 62.8/6.4^(a) Ten/80^(a) 41 142 281 248 6.6/18 42 145270 252 6.8/20 438^(b) 66.8/3.9^(b) Ten/100^(b) 43 149 277 252 6.6/19 44139 277 259 6.6/14 345^(c) 66.3/1.9^(c) Ten/100^(c) 45 150 266 2646.8/15 ^(a)Data was gathered on a combined sample taken from Examples 40and 41. ^(b)Data was gathered on a combined sample taken from Examples42 and 43. ^(c)Data was gathered on a combined sample taken fromExamples 44 and 45.

The data gathered for Examples 38-45 in Table 6 demonstrate both theeffectiveness of solvent removal by the method as measured by the amountof residual ODCB present in the polymer product. Additionally, Dynatuptesting demonstrates the retention of ductility among polymers isolatedby the method.

In Examples 46-53 the extruder devolatilization system was configured asin Examples 38-45. Examples 46-49 were carried out on a 30 percent byweight solution of commercially available ULTEM® 1010 polyetherimide inODCB. Examples 50-53 were carried out on a 30 percent by weight solutionof polyetherimide prepared by chloro displacement having a structurenearly identical to that used in Examples 46-49. The polyetherimide usedin Examples 50-53 was prepared from a 95:5 mixture of 4-chloro- and3-chlorophthalic anhydride. Both polymer-solvent mixtures werestabilized as in Example 5. Data gathered in Table 7 illustrate theefficient separation of the solvent from the polymer-solvent mixture.

TABLE 7 Vacuum Mass Screw Die (mm Hg) Flow Torque speed Pressure BarrelExample V4 V5 V6 (kg/hr) (%) Melt (° C.) (rpm) (kgf/cm²) Temperatures (°C.) 46 711.2 711.2 711.2 30.8 55 367 475 6.5343/325/347/353/352/343/349/335 47 711.2 711.2 711.2 30.8 54 374 475 6.0364/332/350/350/350/351/350/335 48 711.2 711.2 711.2 30.8 54 374 476 6.3366/333/351/349/350/350/350/330 49 711.2 711.2 711.2 30.8 54 375 475 6.3360/333/350/351/350/350/350/330 50 711.2 711.2 711.2 30.8 59 379 475 8.4358/332/350/351/350/349/350/349 51 711.2 711.2 711.2 31.8 59 378 475 8.6353/330/350/351/350/351/350/349 52 711.2 711.2 711.2 31.8 58 378 475 8.4351/332/351/350/350/351/350/350 53 711.2 711.2 711.2 31.8 58 379 475 8.4351/333/352/351/350/351/350/350 Dynatup Energy Number of Feed Residual @Max. Load/ Samples Tank P-valve ODCB by St. Dev. (J) Tested/ Example (°C.) (° C.) % Open^(a) GC (ppm) @100 C. Ductile (%) 46 163 256 /16 — — —47 165 261   /16.2 — — — 48 170 268 /13 438 75.1/3.3^(b) Ten/90^(b) 49168 264 /13 212 50 165 258 /20 387^(c) 65.4/20.9^(c) Ten/90^(c) 51 164260 /20 52 167 258 /20 316 73.8/2.2^(d) Ten/100^(d) 53 167 260 /20 422^(a)Value given is the extent to which the pressure control valve isopen expressed as a percentage of the cross sectional area of the fullyopen valve orifice. ^(b)Data was gathered on a combined sample takenfrom Examples 48 and 49. ^(c)Data was gathered on a combined sampletaken from Examples 50 and 51. ^(d)Data was gathered on a combinedsample taken from Examples 52 and 53.

The polymer product in Examples 48-49 and 51-53 is substantially free ofresidual ODCB. In addition, there were no differences in performance ofthe recovered commercial polyetherimide (Examples 48 and 49) and therecovered chloro displacement product (Examples 50 and 51, and Examples52 and 53) in the Dynatup and ductility measurement test.

In Examples 55 and 56 chloro displacement polyetherimide (M_(w)=62400amu, M_(n)=24200 amu), prepared by condensation of a 25:75 mixture of4-chloro and 3-chlorophthalic anhydride with 4,4′-oxydianiline to affordthe corresponding bisimide followed by chloro-displacementpolymerization reaction with the disodium salt of bisphenol A, wasisolated from a polymer-solvent mixture comprising 30 percent by weightpolymer in ODCB. Example 54 served as a control and employed a 30percent by weight solution of commercially available nitro displacementpolyetherimide, ULTEM® 1010, in ODCB. The solutions were stabilized asin Example 5. The extruder devolatilization system was the same as thatemployed in Examples 46-53. The data gathered in Table 8 illustrate thatthe ductility of the chloro displacement polymer product in Examples 55and 56 is not adversely affected when the method is employed to effectits isolation from ODCB solution.

TABLE 8 Vacuum Mass Screw Die (mm Hg) Flow Torque speed Pressure BarrelExample V4 V5 V6 (kg/hr) (%) Melt (° C.) (rpm) (kgf/cm²) Temperatures (°C.) 54 635 711.2 736.6 31.8 55 376 525 4.2370/334/350/349/351/350/350/351 55 635 711.2 736.6 31.8 58 383 525 9.8373/334/350/351/350/350/352/349 56 635 736.6 736.6 32.2 59 381 525 10.9 344/329/350/350/350/350/348/348 Cracking Feed Pressure Dynatup Energy @Tank P-valve (kgf/cm²)/% Max. Load/St. Dev. Number of Samples Tested/Example (° C.) (° C.) Open (J) @100 C. Ductile (%) 54 150 274 8.9/16 55166 274 9.9/17 66.4/12.0^(a) Ten/100^(a) 56 149 275 8.9/18 ^(a)Data wasgathered on a combined sample taken from Examples 55 and 56.

In Examples 57-59 the present method was applied to the isolation ofpolysulfones from a polymer-solvent mixture. Two polymer-solventmixtures comprising polysulfones were employed. In Example 57 apolymer-solvent mixture comprising 30 percent by weight of a commercialpolysulfone, UDEL-1700 (available from Solvay Advanced Polymers,Alpharetta, Ga., USA), in ODCB was subjected to the present method usingan extruder devolatilization system configured as in Examples 38-45. Noadditional stabilizers were added to the polymer-solvent mixtureprepared from the commercially available polysulfone. In Examples 58 and59 a polymer-solvent mixture was employed which comprised 30 percent byweight polysulfone in ODCB solution, the polymer-solvent mixture beingstabilized as in Example 5. The polysulfone in Examples 58 and 59 wasprepared by reaction of 4,4′-dichlorodiphenylsulfone with the disodiumsalt of bisphenol A in ODCB under standard polysulfone polymerizationconditions. The polysulfone employed in Examples 58 and 59 hadM_(w)=58100 amu and M_(n)=18100 amu. The data in Table 9 demonstratethat the present method is applicable to the separation ofpolymer-solvent mixtures comprising polysulfones, and that theproperties of the product polysulfones so isolated are not adverselyaffected.

TABLE 9 Vacuum Mass Screw Die (mm Hg) Flow Torque speed Pressure BarrelExample V4 V5 V6 (kg/hr) (%) Melt (° C.) (rpm) (kgf/cm²) Temperatures (°C.) 57 711.2 711.2 711.2 31.8 55 384 525 0.84352/332/350/350/350/349/357/331 58 711.2 711.2 711.2 31.8 49 380 525TLTM^(a) 347/330/350/349/350/348/352/330 59 711.2 711.2 711.2 31.8 50383 524 TLTM 352/331/351/350/350/350/350/330 Cracking Feed PressureDynatup Energy Number of Tank P-valve (kgf/cm²)/ Residual ODCB by GC @Max.Load/ Samples Tested/ Example (° C.) (° C.) % Open (ppm) St. Dev.(J)@RT^(b) Ductile (%) 57 161 261 9.8/21 213 — — 58 158 263 9.5/18 —61.1^(c) Ten/100^(c) 59 161 264 9.2/18 196 ^(a)Die pressure was Too Lowto Measure (TLTM) ^(b)RT is room temperature ^(c)Data was gathered on acombined sample taken from Examples 58 and 59.

In Examples 60-65 the present method was applied to the isolation ofpolycarbonate from a polymer-solvent mixture. A polymer-solvent mixturewas prepared comprising 30 percent by weight commercially availablebisphenol A polycarbonate (LEXAN® 120 polycarbonate, available fromGE-Plastics, Mt. Vernon, Ind.) in ODCB. The polymer-solvent mixturecomprising polycarbonate was subjected to the present method using anextruder devolatization system configured as in Examples 38-45 with theexception that no PALL filters were used. No additional stabilizers wereadded to the polymer-solvent mixture prepared from the commerciallyavailable polycarbonate. The data in Table 10 demonstrate that thepresent method is applicable to the recovery of polycarbonate frompolymer-solvent mixtures comprising polycarbonate, and that polymerproduct having very low levels of residual solvent are achievable. Underthe conditions of Examples 60-65, slightly higher levels of residualsolvent were observed in the product polycarbonate than were observed inthe polyetherimide and polysulfone products. This may be due to thelower temperatures employed in Examples 60-65 (melt temperatures300-325° C. versus 375-400° C.). It should be stressed that a very lowlevel of residual solvent has been achieved in Examples 60-65 by thepresent method, the level of residual solvent exceeding 1000 ppmnotwithstanding.

TABLE 10 Vacuum Mass Screw Die (mm Hg) Flow Torque speed Pressure BarrelExample V4 V5 V6 (kg/hr) (%) Melt (° C.) (rpm) (kgf/cm²) Temperatures (°C.) 60 533.4 685.8 685.8 34.0 40 303 550 TLTM^(a)282/266/276/281/282/281/282/277 61 533.4 685.8 685.8 34.0 37 311 550TLTM 332/295/301/300/292/303/307/261 62 533.4 685.8 685.8 34.5 37 308500 TLTM 343/295/300/301/304/300/296/259 63 533.4 685.8 685.8 38.6 37314 500 TLTM 345/295/298/300/307/300/301/261 64 533.4 685.8 685.8 38.633 324 500 TLTM 354/324/329/324/317/323/338/261 65 533.4 685.8 685.838.6 33 325 550 TLTM 358/337/347/329/327/326/320/260 Cracking T feed @ Tfeed after Pressure Residual Feed Tank Heat Exch. (kgf/cm²)/% ODCB by GCExample (° C.) (° C.) P-valve (° C.) Open (ppm) 60 167 274 271 7.0/181934 61 168 274 271 1518 62 160 276 272 6.0/17 1670 63 168 269 2678.5/16 1675 64 169 270 267 8.9/16 1437 65 172 270 267 9.3/16 1385^(a)Die pressure was Too Low to Measure (TLTM).

Examples 66-67 illustrate the application of the present method to theisolation of a polycarbonate ester-polyetherimide blend (Example 67).Two polymer-solvent mixtures were prepared and subjected to the presentmethod. The first, which served as a control, was a 30 percent by weightsolution of ULTEM® 1010 polyetherimide in ODCB. The secondpolymer-solvent mixture was a solution prepared from 22.5 pounds (10.2kg) of ULTEM® 1010 polyetherimide and 7.5 pounds (3.4 kg) of thepolycarbonate ester PCE in 70 pounds (31.8 kg) of ODCB. Each solutionwas stabilized as in Example 5. PCE is a copolycarbonate comprisingbisphenol A residues and iso- and terephthalic acid residues joined byester and carbonate linkages such that repeat units comprising esterlinkages constitute about 60 percent of the weight of the polymer, andrepeat units comprising carbonate linkages constitute about 40 percentof the weight of the polymer. PCE is sold as a blend with polyetherimideunder the trade name ATX200F and is available from GE Plastics. Each ofthe polymer-solvent mixtures was subjected to the present method usingthe extruder devolatilization system employed in Examples 38-45 with theexception that n PALL filter was used in either Example 66 or 67. Thedata in Table 11 illustrate both the low level of residual solventachievable in PCE/polyetherimide blends formed using the present method.In addition, the physical properties of the PCE/polyetherimide blendisolated by the method are consonant with the properties of andidentical blend prepared using conventional extruder melt bendingtechniques.

TABLE 11 Mass Screw Die Vacuum (mm Hg) Flow Torque Melt speed PressureBarrel Temperatures Example V4 V5 V6 (kg/hr) (%) (° C.) (rpm) (kgf/cm²)(° C.) 66 711.2 711.2 711.2 31.8 54 382 525 TLTM356/331/350/350/350/350/351/350 67 711.2 711.2 711.2 31.8 55 370 600TLTM 344/304/321/323/327/329/338/347 Steady-state Cracking RT^(a) IzodImpact Strength Maximum Viscosity @ Feed Pressure Residual (J/m) Tensile350 C. (Pa · s) Tank P-valve (kgf/cm²)/ ODCB by Reverse Un- Strain at100 at 800 Example (° C.) (° C.) % Open GC (ppm) Notched Notched Notched(%) (1/s) (1/s) 66 160 279 11.2/15 37.4 900.9 1378.8 26.81 1856 1018 67162 259 12.1/16 327 58.7 2987.7 3713.4 34.95 1441 752 ^(a)RoomTemperature Izod Impact Strength

Examples 68-73 were carried out using two polymer-solvent mixturescomprising about 15 weight percent and about 30 weight percent ULTEM®1000 polyetherimide in anisole (See column heading “Solids %”). Theextruder devolatilization system used was analogous to that used inExamples 38-45 but included a second side feeder at barrel 2, anadditional extruder barrel and two additional vents for solvent removal.The second side feeder was located on the opposite side of the extruderdirectly across barrel 2 from the first side feeder. Atmospheric ventswere located at barrel 1 (V1), on the first side feeder (V2), on thesecond side feeder (V3) and at barrel 5 (V4). Vacuum vents were locatedon barrel 6 (V5), barrel 8 (V6), barrel 10 (V7) and barrel 11 (V8). Theextruder itself was a 40 mm diameter, co-rotating, intermeshingtwin-screw extruder having a length to diameter ratio (L/D) of 44. Theextruder screw elements were configured analogously to the configurationused in Examples 38-45 with melt seal generating elements located at theupstream edge of barrel 6, the downstream edge of barrel 7 and at thecenter of barrel 9. The polymer-solvent mixture was introduced into thefeed zone of the extruder through a pressure control valve at thedownstream edge of barrel 2. Solvent removed through the atmosphericvents (V1-V4) was collected at a first series of condensers. Solventremoved through vacuum vents (V5-V8) was collected at a second series ofcondensers. As in earlier Examples it was noted that most of the solventwas recovered through the atmospheric vents (V1-V4) (See column heading“Solvent Flashed Upstream (% of total)” in Table 12). The data in Table12 illustrate that very low levels of residual anisole can be achievedusing the present method, even at very high polymer-solvent mixture feedrates. It should, however, be noted that because of the high melttemperatures of Examples 68-73, the molecular weight or other physicalproperty of the polymer product may be significantly different from thepolymer initially present in the polymer-solvent mixture. Samples takenfrom the polymer product in Examples 68-73 showed up to a 12 percentincrease in molecular weight and up to a 90 percent increase inviscosity relative to an ULTEM® 1000 polyetherimide control which wasnot subjected to the isolation by the present method. For a givenpolymer system, the optimum melt temperature which balances residualsolvent level against the preservation of polymer physical propertiescan be readily determined by experimentation.

TABLE 12 Polymer- Solvent Solvent Low-shear Mixture Flashed Rate ScrewFeed Upstream Residual Viscosity @ Speed Rate Melt P-valve (% of Anisole340° C. Example (rpm) (kg/hr) (° C.) Solids % (° C.) total) (ppm)Mw/Mn/PDI (P) 68 500 204 468 16.7 240 78 113 69 500 156 469 15.7 254 9022 70 500 46.7 30 222 <5 59900/21840/ ~71000 2.74 71 500 130 480 30.6248 85 105 54760/21860/ 48000 2.51 72 500 155 478 30.9 247 84 <556960/22130/ ~61000 2.57 73 500 238 482 31.1 226 88 195 55500/22720/51100 2.44 Control^(a) 53690/22910/ 37200 2.34 ^(a)ULTEM ® 1000polyetherimide

In Examples 74-75 two different grades (Grades#1 and 2) of commerciallyavailable ULTEM® polyetherimide were dissolved in ODCB to formpolymer-solvent mixtures comprising 30 percent by weight polyetherimide.The solutions were subjected to extruder devolatilization according tothe present method and the polyetherimides were recovered. Examples 74and 75 were carried out on an 8-barrel, 5-vent extruder and a 10 barrel6 vent extruder respectively. The conditions employed in each case wereessentially the same as in Example 39. The recovered polyetherimideswere subjected to a battery of physical tests and the results werecompared with the results of the same tests carried out on samples ofthe same grade of ULTEM® polyetherimide which had not been subjected toextruder devolatilization (See “Commercial Controls”, Table 13). Dataare gathered in Table 13 which show no significant impact of extruderdevolatilization according to the present method on the properties ofthe product polyetherimide.

TABLE 13 EXAMPLE ULTEM ® ULTEM ® 1010 74 1010 75 Grade#1 Grade#1 Grade#2Grade#2 Comments Commercial Extrusion Commercial Extrusion Controlisolated Control isolated Molecular Weight and Residual Solvent M_(w)(1000's) 44.7/43.8 44.3 44.4 44.2 M_(n) (1000's) 19.6/19.2 19.4 19.719.6 PI 2.28/2.27 2.28 2.25 2.25 ODCB (ppm) 344 369 Rheology η_(o) at340° C. (P) 17100 16800 18000 17000 Color/Visual Solution YI 15.8 11.912.5 Thermal T_(g) (° C.) 217.0 216.5 216.6 215.3 Mechanical DynatupImpact @ 100° C. Total % Ductile 100 100 100 100 Energy @ Max 63.6 65.270.8 66.4 Load (J) Standard Deviation 2.3 0.94 3.3 1.4 (J)

Thus, the polyetherimide recovered from the polymer-solvent mixture hasessentially the same physical characteristics as the commercial product.In Table 13 molecular weight data for the “Commercial Control” “Grade#1”is given as a range of molecular weights. Thus, the significance of“44.7/43.8” is that the weight average molecular weight of the grade#1commercial control may vary from about 43,800 amu to about 44,700 amu.The Dynatup measurements are reported as the average value from 10measurements.

Comparative Examples 1-7 illustrate extruder devolatilization of apolymer-solvent mixture using an alternate extruder configuration. InComparative Examples 1-7 the system used to perform the devolatilizationwas a 10 barrel, 25 mm diameter, co-rotating, intermeshing twin-screwextruder having an L/D of 40. The extruder had 5 vacuum vents (V1-V5)located at barrels 1, 3, 5, 7, and 9 respectively. The upstream vacuumvents (V1) and (V2) were operated at relatively low vacuum (vacuum gaugereading of about 5 to about 10 inches of mercury or about 127.0 to about254 mm Hg). Vacuum vents (V3), (V4) and (V5) were operated under highvacuum (vacuum gauge reading of about 29 inches of mercury or about736.6 mm Hg). Solvent vapors removed through vacuum vents (V1) and (V2)were collected separately from solvent vapors removed through vents(V3), (V4) and (V5). The polymer-solvent mixture used was a 30 percentby weight solution of ULTEM® 1010 polyetherimide. In ComparativeExamples 1-7 the polymer-solvent mixture was transferred by nitrogen gaspressure from a heated feed tank held at 180° C. to a gear pump whichforced the hot polymer-solvent mixture through a pipe which was hardplumbed to the feed inlet of the extruder. Data are presented in Table14 which demonstrate that because there is no superheating of thepolymer-solvent mixture prior to its introduction into the extruder lowfeed rates and relatively high melt temperatures are required in orderto achieve low levels of residual ODCB in the recovered polymer. Thus,the method of separating a polymer-solvent mixture using the method ofComparative Examples 1-7 is shown to be less efficient than the presentmethod.

TABLE 14 Polymer- Extruder Solvent Residual Molecular Barrel MixtureScrew Die ODCB Weight(Mw/ Comparative Temp. Feed Rate Speed TorquePressure Melt by GC 1000)^(a) (1 St. Example (° C.) (kg/hr) (rpm) (%)(kgf/cm²) (° C.) (ppm) Dev.) CE-1 350 6.8 325 36 14.1–17.6 394 121 45.57(0.28) CE-2 350 11.3 325 43 21.1–24.6 394 342 44.33 (0.18) CE-3 350 11.3500 40 14.8–17.6 414 542 45.81 (0.59) CE-4 400 6.8 350 — — — 102 45.77(0.78) CE-5 400 11.3 350 39 61.2–65.4 409 204 45.05 (0.03) CE-6 400 11.3450 36 45.7–52.0 423 201 45.72 (0.56) CE-7 400 13.4 550 37 36.9–43.9 439210 46.33 (0.26) ULTEM ® 1010 45.44 (0.73) Control ^(a)Mean of threedeterminations.

Examples 76-77 were prepared to illustrate the isolation of apolyetherimide-polyphenylene ether blend from an ODCB solution ofpolyetherimide and polyphenylene ether. The solution for Examples 76-77was prepared from a stirred mixture containing 24 pounds (10.9 kg) of0.46 IV PPO, 36 pounds (16.3 kg) of ULTEM® 1010, lot UD9796 and 140pounds (63.5 kg) of ODCB. The solution was maintained in a heated feedtank at about 160° C. under a nitrogen atmosphere (80-100 psig N₂ or5.6-7.0 kilogram-force per square centimeter (kgf/cm²)). A feed streamof solution was continuously fed to an extruder from the tank using agear pump. The extruder used was a 25 mm diameter co-rotating,intermeshing extruder of the twin-screw type comprising 10 barrels(L/D=40) and six vents for the elimination of volatile components. Thesolution was fed to the extruder at the downstream edge of barrel number2. Solvent removal occurred through the six vents located at barrelnumbers 1 (V1), 2 (on a side feeder, V2), 4 (V3), 5 (V4), 7 (V5) and 9(V6). (V3-V6) contained Type C vent inserts. Vents (V1-V2) were operatedat about atmospheric pressure and vents (V3-V6) were operated at about711 millimeters of Hg of vacuum. The vents were connected to a solventremoval and recovery system. Conveying elements were used under the feedport and all of the vents. Left-handed kneading blocks were positionedbefore vacuum vents (V4) and (V6) to seal the screw, and narrow-diskright-handed kneading blocks and neutral kneading blocks were positionedin barrels 2 and 3. Finally, the air cooling manifold and barrel heaterson the extruder were turned on during the experiment to achieveisothermal conditions.

The process was run at about 39.5 lb/hr (17.9 kg/hr) of solution (90 rpmof pump speed), 403 rpm extruder screw speed, and 34-35% of drivetorque. The polymer was extruded through a 2-hole die plate andpelletized. The processing conditions for Examples 76-77 are provided inTable 15.

TABLE 15 Solution Mass Residual Flow Screw T of feed ODCB Rate TorqueMelt T speed Die Pressure Actual Barrel in tank by GC Example (kg/hr)(%) (° C.) (rpm) (kgf/cm²) Temperatures (° C.) (° C.) (ppm) 76 17.9 34354 403 4.0 355/326/331/331/329/ 161 333/324/330 77 17.9 35 350 403 2.5356/325/330 × 2/329/ 163 1204 328/322/330

Scanning electron microscope (SEM) images (FIGS. 3 and 4) of twodifferent samples of extruded material show a uniform dispersion ofpolyphenylene ether particles of about one micrometer in a continuousphase of polyetherimide. This result is surprising considering thatthere was limited mixing of the materials in the extruder due to themild screw design and reduced residence time of the polymer in theextruder. The uniform dispersion of the polyphenylene ether was effectedin the stirred tank used to prepare the solution.

Examples 78-80 were prepared to illustrate the isolation of apolyetherimide-fumed silica composite from an ODCB solution ofpolyetherimide and fumed silica. The solution for Examples 78-80 wasprepared from a stirred mixture containing 28 pounds (12.7 kg) of ULTEM®1010, lot UD9796, 72 pounds (32.7 kg) of ODCB, 2.8 pounds (1.3 kg) offumed silica 88318 manufactured by GE Silicones, Waterford , N.Y., and20 pounds (9.1 kg) of ODCB used to wet the fumed silica prior to itsaddition into the tank. The solution was maintained in a heated feedtank (about 165° C.) while a feed stream of solution was continuouslyfed to an extruder from the tank using a gear pump. The extruder usedwas a 25 mm diameter co-rotating, intermeshing extruder of thetwin-screw type comprising 14 barrels (L/D=56) and six vents for theelimination of volatile components. The solution was fed to the extruderat the upstream edge of barrel number 4 through a port designed forliquid injection. Solvent removal occurred through the six vents locatedat barrel numbers 1 (V1), 5 (V2), 7 (V3), 9 (V4), 11 (V5) and 13 (V6).Vents (V1-V4) contained Type C vent inserts. Vents (V1-V4) were operatedat about 711 millimeters of Hg of vacuum (house vacuum system) whilevents (V5-V6) were operated at about 737 millimeters of Hg of vacuum(vacuum pump). Vent (V2) plugged immediately upon start up of the run.The vents were connected to a solvent removal and recovery system.Conveying elements were used in the extruder screws under the feed portand all of the vents. Kneading blocks were used in the extruder screwsin the zones between all of the vents.

The process was run at about 43.8 lb/hr (19.9 kg/hr) of solution, 309rpm extruder screw speed, and 83-84% drive torque. The filled polymercomposite was extruded through a 2-hole die plate and pelletized. Theextrudate contained about 9.1 percent by weight fumed silica based onthe total weight of the composite. The processing conditions forExamples 78-80 are provided in Table 16.

TABLE 16 Solution Mass Flow Screw T of feed Rate Torque Melt T speed DiePressure Actual Barrel in tank Example (kg/hr) (%) (° C.) (rpm)(kgf/cm²) Temperatures (° C.) (° C.) 78 19.9 84 387 309 TLTM^(a)313/353/340/349/350/ 164 350/350/349/349 79 19.9 83 389 309 TLTM316/350/340/350 × 3/ 163 349/350/351 80 19.9 84 389 309 TLTM318/350/340/350 × 6 166 ^(a)The pressure transducer at the extruder dieplate may have been damaged, which may have caused it to read a lowpressure for the duration of the experiment

The Dynatup tests were conducted on the composite material using thestandard ASTM D3763 method (conducted at 100° C.) on plaques molded fromthe extruded, pelletized product polyetherimide-fumed silica. The columnheading “Dynatup Energy @ Max. Load/St. Dev. (J) @100C” gives theaverage Dynatup test value in joules and standard deviation obtainedfrom the testing of ten molded plaques prepared from the isolatedpolyetherimide-fumed silica composite. The results from the testing ofthe composite (PEI-fumed silica) and a control sample of ULTEM® 1010 lotUD9796 is provided in Table 17.

TABLE 17 Dynatup Energy Total Number @ Max. Energy/St. of SamplesLoad/St. Dev. Dev. (J) Tested/ CTE Example (J) @100 C. @100 C. Ductile(%) (1/° C.) PEI-fumed 55.9/13.6 76.5/9.4 Ten/100 38.9 × 10⁻⁶ silicaULTEM ® 82.6/9.4  89.2/7.7 Ten/50  66.4 × 10⁻⁶ 1010

The results of a ductility study of the composite material and thecontrol sample of ULTEM® 1010 is shown in Table 17. It should be notedthat the ductility of ULTEM® 1010 of 50% at 100° C. is atypical for thisresin as it normally is around 100% when tested under these conditions.

Also provided in Table 17 is the coefficient of thermal expansion forthe isolated polyetherimide-fumed silica material as well ascommercially available ULTEM® 1010. Samples were tested using a PerkinElmer TMA7 thermomechanical analyzer. These results highlight thebeneficial effect of using fumed silica to reduce the expansioncoefficient of the polyetherimide.

FIG. 5 is a graph of rheology data for the isolated polyetherimide-fumedsilica composite as well as a control sample of ULTEM® 1010. FIG. 5provides viscosity data based on samples cut from injection moldedDynatup plaques, and tested using low-amplitude oscillatory measurementson a Rheometrics RDAIII rheometer. The samples were dried in a vacuumoven for 2 days at 170° C. prior to testing, molded into disks at 320°C., and dried an additional 2 days at 170° C. The results indicate thatthe silica-filled polymer was more viscous than the unfilled resin,particularly at the lower deformation rates (frequencies) investigated.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood by thoseskilled in the art that variations and modifications can be effectedwithin the spirit and scope of the invention.

1. A method of preparing a filled polymer, comprising: introducing aheated mixture comprising polymer, filler, and solvent to an extruder,wherein the extruder comprises an upstream vent and a downstream vent;and removing solvent from the heated mixture via the upstream vent andthe downstream vent to form a filled polymer comprising the fillerdispersed therein; wherein the polymer of the heated mixture and of thefilled polymer is polyetherimide, polycarbonate ester, poly(aryleneether), polyamide, polyester, polysulfone, polyetherketone, polyimide,polysiloxane, liquid crystalline polymer, or a combination comprising atleast one of the foregoing polymers.
 2. The method of claim 1, whereinthe filler is fumed or fused silica; crystalline silica; talc; glassfibers; carbon black; conductive fillers; carbon nanotubes; nanoclays;organoclays; or a combination comprising at least one of the foregoingfillers.
 3. The method of claim 1, wherein the extruder furthercomprises a side feeder, wherein the side feeder comprises a side feedervent operated at about 750 mm of Hg or greater or about 750 mm of Hg orless, and wherein the side feeder further comprises a kneading block. 4.The method of claim 1, wherein the filler is present in the filledpolymer in an amount of up to about 50 weight percent based on the totalweight of the filled polymer.
 5. The method of claim 1, wherein thefiller is present in the filled polymer in an amount of up to about 20weight percent based on the total weight of the filled polymer.
 6. Themethod of claim 1, wherein the solvent is a halogenated aromaticsolvent, a halogenated aliphatic solvent, a non-halogenated aromaticsolvent, a non-halogenated aliphatic solvent, or a combinationcomprising at least one of the foregoing solvents.
 7. The method ofclaim 1, wherein the amount of polymer and filler in the mixture is lessthan or equal to about 75 weight percent based on the total weight ofthe mixture.
 8. The method of claim 1, wherein the amount of polymer andfiller in the mixture is about 5 to about 60 percent by weight based onthe total weight of the solids mixture.
 9. The method of claim 1,wherein the mixture is superheated prior to introducing the mixture tothe extruder.
 10. The method of claim 9, wherein the mixture issuperheated to a temperature of about 2° C. to about 200° C. higher thanthe boiling point of the solvent at atmospheric pressure.
 11. The methodof claim 1, wherein about 50 to about 99 percent of the solvent presentin the mixture is removed through the upstream vent.
 12. The method ofclaim 1, wherein about 1 to about 50 percent of the solvent present inthe mixture is removed through the downstream vent.
 13. The method ofclaim 1, wherein the upstream vent is operated at about 750 mm of Hg orgreater or about 750 mm of Hg or less, and wherein the downstream ventis operated at about 750 mm of Hg or less.
 14. The method of claim 1,wherein the extruder is operated at a temperature of about 200 to about400 degrees centigrade.
 15. The method of claim 1, wherein the upstreamvent is positioned upstream from a feed inlet.
 16. The method of claim1, wherein the extruder comprises one or more additional downstreamvents.
 17. The method of claim 16, wherein the extruder comprises aconveying element under a feed inlet and under the vents; and a kneadingblock in the zones between the vents.
 18. A method of preparing a filledpolymer, comprising: introducing a heated mixture comprising polymer,filler, and solvent to an extruder, wherein the extruder comprises anupstream vent and two or more downstream vents, and wherein the extruderoptionally comprises a side feeder operated as a side vent; removingsolvent from the heated mixture via the upstream vent and the downstreamvents to form a filled polymer comprising the filler dispersed therein,wherein the filler is present in the filled polymer in an amount of upto about 50 weight percent based on the total weight of the filledpolymer; and wherein the polymer of the heated mixture and of the filledpolymer is polyetherimide, polycarbonate ester, poly(arylene ether),polyamide, polyester, polysulfone, polyetherketone, polyimide,polysiloxane, liquid crystalline polymer, or a combination comprising atleast one of the foregoing polymers.
 19. A filled polymer prepared bythe method of claim
 1. 20. The method of claim 1, wherein the polymerfurther comprises polycarbonate, poly(alkenyl aromatic), or acombination thereof.